1-Page Summary

How do you lose weight? Eat less than you’re burning each day.

It's simple. But simple doesn’t mean easy. Like anything else in life, successfully losing weight requires:

Calories In/Calories Out

The way to lose weight is to eat fewer calories than you’re burning each day.

Everyone has a different daily calorie requirement based on height, weight, and activity level. Very roughly, the average man burns around 2000 calories, and the average woman around 1500 calories. Determine yours with this calculator.

A pound of fat contains about 3500 calories. Losing a pound of fat requires you to burn 3500 more calories than you eat. There’s no way around this. Fad dieting techniques like keto, paleo, intermittent fasting, etc. are all merely different ways of restricting your calorie intake.

Likewise, eating an extra 250 calories a day causes you to gain a pound in 2 weeks. Or 26 pounds a year. And this just requires one more helping at dinner, one beverage per day.

For purposes of weight loss, you could eat 1500 calories of butter a day and still lose weight. It’s not what you eat, it’s how much of it.

The Eat Watch

Imagine that you had a watch that told you when to eat. When it flashed Eat, you would eat. When you reached your calorie limit for the meal or the day, the watch would stop flashing, and you’d stop eating.

People who have been skinny their entire lives have perfectly tuned Eat Watches. When they eat over their caloric requirement for the meal, they simply stop eating. Eating past this point becomes unbearably uncomfortable.

People who gain weight easily have broken Eat Watches. Cutting calories is painful; eating excess calories is easy. It might even be easy for you to keep eating past the point of discomfort.

But this doesn’t mean you’re doomed for life. Many of us are born with bad vision, but you can get glasses to correct your problem. If you have a broken Eat watch, you can build your own artificial one, by tracking your weight and calories.

Tracking Weight

If you’ve ever tried to lose weight and measure your body, the path your body takes is startling.

The reason for this wild fluctuation is water, influenced by salt intake. This is NOT solid body mass. Because a pound of fat requires 3500 calories, there is simply no way to gain 3 pounds of fat in a day.

At a rate of undereating 500 calories per day (which is already viscerally difficult), you lose less than 0.2 pounds of fat a day. This signal is largely lost in the noise of day-to-day weight fluctuations.

The solution to this is the exponentially weighted moving average (EWMA). This takes a moving average to smooth out daily fluctuations, and weighs recent data more strongly than past data.

The trend of the EWMA shows weight loss per week, which can then be calculated into calorie deficit per day.

Meal Planning

Pre-planning meals — how much you eat AND when — gives you a reliable daily calorie intake. If you eat only what you plan to, then you’re guaranteed to achieve your goal. (Again, simply, not necessarily easy).

You would never invest in a company that sets no budgets and whose strategy is “spend whatever we feel like day to day, and hope it’ll work out in the long run.” Not only would this be more likely to fail than methodical planning, there’d be no way to measure actual performance against goals to figure out the problems. “Winging it” in relation to your eating target is the same.

Tips:

The Weight Loss Journey

If you have little knowledge of calorie content of foods, and tracking weight is new to you, it may be wise to spend a couple of weeks just getting used to the actions — monitoring your daily weight and measuring your calorie spend. Once you’ve become accustomed to your weight fluctuations and the procedures, you’ll be better equipped to execute your plan.

Start your diet in a regular period when you have a regular schedule, when you have time to adjust to the diet.

The first 3 days are the hardest as your body adjusts to burning fat. You’ll feel cold, weak, irritable, tired, and a constant gnawing hunger. It is this bad, and it’s not good to sugarcoat this — better for you to know what will come and handle it better. But rest assured, it will never feel worse than this. The hunger softens from an aching pain you think about constantly, to a minor annoyance that becomes a fact of life.

Start your weight loss during a regular period of time when you have a regular schedule, ideally of at least 2 weeks of “normal life.” Maintaining a weight loss plan benefits from momentum and “getting in the groove.” During a vacation, extensive travel, or holidays, it’s hard to maintain the discipline your plan requires.

Once you hit your target weight, give yourself some buffer by getting your average weight trend line by 2 pounds under your target weight.

Then, once you’re ready to stop your weight loss, transition back to maintenance calories slowly, perhaps adding 100-200 calories back per week. Adding back too much at once might cause a weight spike.

Perfect Weight Forever

Because your eating control system is broken, you need to continue with tracking weight and meal planning indefinitely. People yo-yo between weight loss and weight gain because they fall back into their previous bad habits.

Set hard limits to your weight that require dialing back calories. 2 pounds of your weight target is a soft wall requiring calorie adjustment; 5 pounds of your weight target is a hard wall requiring immediate resumption of your previous dieting plan.

Luckily it gets easier with more time — you gain an intuition for calorie content, you don’t overeat or binge as much, and your body adjusts.

1: How to Lose Weight

There’s a story about financial traders on Wall Street. A novice asks a guru, “How do you make money in the market?”

The guru responds, “It’s simple: buy low, sell high.”

The beginner replies, “How can I learn to do that?”

The guru responds, “Ah — that takes a lifetime.”

Simple doesn’t mean easy.

How do you lose weight? It’s simple. Eat fewer calories than you’re burning each day. But simple doesn’t mean easy.

What weight loss really requires is:

This is what’s needed in any of life’s hurdles. This is precisely what losing weight achieves.

The author is John Walker, founder of software company Autodesk. He spent most of his life fat, before figuring out how the body and weight loss works. Then, in less than a year, he lost 60 pounds and kept it off forever.

This book is an engineer’s approach to weight loss, described in terms of control systems, feedback loops, measurement noise reduction, and practical problem-solving.

In the first 4 chapters, we’ll discuss the fundamentals of a successful weight loss plan. Then we’ll discuss the practicalities of starting the weight loss plan. Finally, we’ll discuss what to do when you reach your goal weight and keep it off for good.

Motivation

If you’ve tried diet after diet and failed each time, what motivates you to try again?

This book will lay out a program that makes the steps easy, and the thought of failure hard to imagine. It explores the principles of weight that other fad diets ignored, which caused you to avoid addressing the root cause. After reading this, you should think, “Hey, this isn’t hard at all! I can do this!”

And the goal is worth it. Within months, people will find it hard to imagine you as overweight. You’ll be able to walk up stairs without noticing the exertion. Once you’ve experienced the joy and confidence, you’ll never consider giving it up.

Health and weight loss are rewards that no amount of money, no degree of knowledge can buy.

Calories: It’s Simple

The human body is a simple system. Everyday, your body needs energy to function — to keep the body warm, to generate new cells, to think. Energy is usually measured in calories.

You eat food to gain energy. Your weight change depends directly on how many calories you eat, and how many calories you burn.

(Shortform note: To make sure you understand this, here’s an analogy: consider a fireplace that burns wood at a particular rate.

This is the basis of “Calories In Calories Out.” This is an inviolable rule that applies to every living thing.

The number of calories you burn each day depends on a few factors: 1) your height and build, 2) your activity level, 3) your gender. Very generally, the average normal-weight man burns about 2000 calories a day; the average woman about 1700 calories. If you’re taller than average, have a physically demanding job, exercise a lot, or are overweight, you burn more than this. Take the opposite of all of these—if you’re shorter, sit most of the day, don’t exercise, and are underweight—and you burn less than this.

To lose one pound of fat, you need to burn 3500 calories more than you eat. Let’s say you burn 1800 calories a day. If you eat 500 fewer calories each day (1300 calories), you will lose one pound each week.

Likewise, to gain one pound of fat, you need to eat 3500 calories more than you burn. This is not hard to do. 2 cans of beer have 300 calories; one donut has 250 calories. If you ate one donut’s worth of calories each day above what you normally burn, you would gain 1 pound every 2 weeks. In a year, you would gain 26 pounds.

Again, weight loss is simple in principle. To lose weight, you need to eat fewer calories than you burn each day. To maintain your ideal weight, you need to eat the same number of calories as you burn each day. Anyone who practiced both regularly would be at their ideal weight for the rest of life.

Shortform Exclusive: What Are Fad Diets Doing?

(There’s some confusion about how fad diets don’t require counting calories but still allow for weight loss.

No matter what diet you use, there is no escaping Calories In, Calories Out. To do otherwise would be to violate “conservation of energy,” one of the physical laws of the universe.

Most fad diets don’t talk about this principle because they want their diets to seem more magical than they really are. If they said, “with our diet, you’ll lose weight by reducing your daily calorie intake, which you could do by yourself and your own diet” they would sell a lot fewer subscriptions.

But fad diets do help some people lose some weight, for some period of time (many fall off the diet and regain the weight). It might have done this for you. So for some period of time, the fad diet was causing you to eat less without your having to think about it. Here are the general ways they work:

This is by and large true. The major difference is that you don’t necessarily absorb all the calories that you eat. For instance, if you have issues with gut health, you’ll tend to absorb fewer calories than people with healthy guts. But for most people, Calories In, Calories Out is by and large true.)

Does What You Eat Matter?

So far we haven’t focused on nutrition. That’s because, for the purposes of weight loss, what you eat matters far less than the calories that you eat. You could lose weight by eating a diet entirely of butter, as long as you’re running a calorie deficit.

Of course, if you can, it’s better to eat a more nutritious diet, balanced among the major macronutrients: carbs, proteins, and fats. It’s also better to get sufficient vitamins in your diet. If you eat a varied diet, it’s very unlikely you’ll run short of a vitamin — if you’re worried, just eat a multivitamin.

(Shortform note: This is true assuming you can methodically stay under the calorie target. But for many of us, what you eat also affects how much you want to eat:

If It’s So Simple, Why’s It So Hard?

It’s hard to lose weight today because millions of years of biological evolution are working against us.

For most of the world’s history, it was hard to get enough food to survive. Human tribes might go weeks between a big hunt. Sudden droughts might kill off plants that we ate.

So we evolved behaviors to get through periods of famine. After your tribe brings back a woolly mammoth, you eat all the calories you can to stockpile up fat to survive through harsher times. This means that whenever you see an excess of food, you tend to want to eat as much as you can.

The problem with today’s environment is that food is always readily available. Unlike millions of years ago, most people will find it extremely hard to starve to death.

But your survival signal is still pinging all the time, urging you to eat more. Some of us have stronger such signals than others. So while your rational brain knows you should be of lean weight, your animal brain wants to stockpile all the calories it can, to last through a famine that will never come.

Unfortunately, to lose weight, you will need to go hungry. As we’ll discuss later, your body has a calorie setpoint that it expects; deviating under this will set off the hunger signal. Rest assured, this pain is temporary and won’t last forever — you won’t be hungry when you’re maintaining weight.

It’s Hard to Exercise the Pounds Away

So you need to run a calorie deficit to lose weight. In the Calories In, Calories Out model, one part of the equation is how many calories you eat. Can you change how many calories you burn per day?

By far, most of what your body is burning each day is used for daily maintenance. It takes a lot of energy to stay warm at 98.6°F, to power your brain, and to keep your cells healthy.

It’s tempting to think about adding on exercise to burn the food away. You might know an athletic person who seems to be able to eat whatever they want and never worry about their weight. Maybe you could do that too!

But let’s examine the calories burnt. An hour of walking burns only 300 calories per hour. Swimming, 400 calories per hour; tennis 500 calories per hour; jogging 700 calories per hour.

These numbers look pretty big, maybe enough to outweigh that extra slice of pie you want to eat. But do you remember the last time you sustained activity for a full hour without stopping? And can you really do this, every single day of the week, without fail?

In contrast, compare that to calories from food: 6 Oreo cookies have 300 calories; a Snickers bar, 275 calories; medium fries at McDonald’s, 340 calories. Is it easier to not eat a medium fries, or to jog for half an hour? Most people would say the former.

Furthermore, many people cancel out their activity by eating more to compensate. Feel good about running a mile? Add a little more peanut butter to your sandwich.

By far, most people who are successful at losing weight do it by controlling their eating. In most people’s experience, it’s easier to lose 500 calories per day by eating less than to burn it through exercise.

This isn’t to say that exercise is unimportant. It’s good for your body and has benefits beyond weight loss, as we’ll discuss at the end of the book. But don’t think that exercise can do the whole job. You’ll likely end up disappointed and abandon the whole program.

2: Eating’s Feedback Loops

Wouldn’t it be great to have a watch that tells you when to eat and when to stop? When it says EAT, you can eat. It’d monitor what you’re eating, track calories for you. Then when it figures out you’ve had enough calories for the meal to keep your weight, it says STOP, and you stop eating. The Eat Watch would be smart enough to keep you at your daily calorie limit for your ideal weight.

Some people are born with a natural, built-in eat watch that works perfectly. Let’s call this type of person Skinny Stable Sam. They eat only the amount needed to maintain their thin bodies, for their entire life. If they eat less than what they burn, they get hungry and they eat. If they overeat in a meal, they feel uncomfortable and take longer to get hungry again, plus they eat less in a later meal. Their point of discomfort and satiety is set precisely at what their body needs.

If you’re overweight, your Eat Watch is broken in a way that causes you to gain weight over time. Let’s say that your ideal weight requires 1600 calories.

(Shortform note: Other factors also play a role in setting your Eat Watch. Sleep deprivation and high stress make you tend to eat more, as a biological response to a stressful dangerous environment. Addictive foods manipulate your Eat Watch and confuse you about the calorie content if what you’re eating.)

Unlike Skinny Stable Sam, you were born with a broken Eat Watch. But this doesn’t mean you’re screwed for life.

Many of us are born with bad vision, but you can get glasses to correct your problem. If you have a broken Eat watch, you can build your own artificial one, by tracking your weight and calories.

3: Measuring Weight

Tracking calories is critical — it’s easy to overeat, and having a strict boundary will make it less likely for you to eat past your goal. And if you perfectly measure your calorie intake, then it should correspond well with your weight loss.

But how many calories you’re eating isn’t your final goal — your weight is. Your weight keeps you honest — if you’re not losing pounds as quickly as you think you should be, then you’re probably eating more than you think, or you burn fewer calories than you estimated. Either way, you need to adjust.

If you’re serious about losing weight, you should measure your weight everyday. To do otherwise is to try to drive without looking at the road. Would you drive by looking at the road for 1 second, then covering your eyes for 4 seconds before looking again?

The Typical Weight Loss Path

If you’ve ever tried to lose weight and measure your body, the path your body takes is startling.

No wonder you’re afraid to step on the scale! It’s like a slot machine of punishment.

The reason for this fluctuation is water. Any real weight loss (i.e. loss of fat) will happen with less than 0.3 pounds per day — and this corresponds to a high 1000 calorie deficit, which is more difficult than most can sustain. Any variation that happens beyond 0.3 pounds is almost entirely water.

Charting Weight Loss

As a result, your day-to-day weight can be volatile. On some days, you lose 3 pounds, and it feels like a huge victory. On others, you gain 3 pounds, and it feels like all your effort was for nothing. Here’s what a weight chart looks like:

hackers-diet-weight-chart.png

So there are high day-to-day fluctuations. But what you really care about is finding the underlying trend — how much weight are you really losing, day to day?

The answer lies in a technique that stock traders use to figure out trends from the minute-to-minute noise: the exponentially weighted moving average. In simple terms:

Applied to the very same weight chart above, the EWMA produces this much smoother line:

hackers-diet-weight-chart-ewma.png

Wouldn’t following the orange line feel much less volatile and let you keep your sanity? Large drops in weight still move the trend line down, but their impact is blunted by the weighting. Likewise, one-day spikes in weight after a cheat meal don’t budget the trend line that much.

If you continuously lose weight, think of today’s weight as a sinker, dragging the trend down.

This average line is also useful when you’ve reached your goal weight and want to prevent reversions. This lets you detect a gradual uptrend in your weight, even while your day-to-day weight fluctuates.

Technical Details About EWMA

The details of setting up exponentially weighted moving averages are out of scope of this summary, but the author provides weight tracking spreadsheets here. If you’re curious, you can learn the details of the math here.

If you do set up an EWMA, the author recommends a smoothing value of 0.9 can be aligned with a shift of about 10.

4: Planning Meals

Pre-planning meals — how much you eat AND when — gives you a reliable daily calorie intake. If you eat only what you plan to, then you’re guaranteed to achieve your goal. (Again, simply, not necessarily easy).

You would never invest in a company that sets no budgets and whose strategy is “spend whatever we feel like day to day, and hope it’ll work out in the long run.” Not only would this be more likely to fail than methodical planning, there’d be no way to measure actual performance against goals to figure out the problems. “Winging it” in relation to your eating target is the same.

Rigid planning of meals, and adherence to the plan, is the most important strategy in losing weight. You will lose some spontaneity of your eating, but you will be rewarded by weight loss.

Planning meals has these benefits:

Pointers on Planning Meals

What you eat doesn’t matter as much as how much you eat. Calories per day is by far the most important number as far as weight is concerned. What doesn’t matter as much: the composition of what you eat (such as fats vs carbs vs protein), and when you eat it.

So in general, keep your current eating schedule. You can eat 3 meals a day, or 8 small meals. But keep a regular schedule.

Keep your diet composition the same as your normal diet. Eat the same things—just change the amounts to keep under the calorie limit.

Be very aware of serving sizes. It’s easy to overeat. The safest option is to measure out exactly what you planned — 100g of chicken breast, 1 tbsp of mayonnaise, 2 oz. of potato chips. Otherwise, it is very easy to eat over your allotment. The first time you measure calorically dense foods like cookies, nuts, and meat, you will be shocked by how many calories are contained in tiny amounts of food.

An easy way out: eat only pre-prepared foods, like microwavable meals, meal kits, or liquid meals like Slimfast. Not only does this make it easier to restrict calories, it also lets you eat on schedule without time-consuming prep.

The author recommends a few “secret weapons” in your diet that make hunger easier to deal with:

While measuring and scheduling all your food is laborious at first, quickly you will develop an intuition for how many calories a certain amount of food contains.

Eating out adds variability to your planning since you can’t control the preparation of food.

5: Starting to Lose Weight

We've now covered all the critical knowledge and tactics needed to lose weight. Now we formally put it together into a feedback loop system that controls your weight:

If you’re losing less weight than you expect, there are only two possibilities. Either you’re burning fewer calories than you expected, or you’re eating more calories than you budgeted, or both. Analyze your situation, and adjust accordingly.

hackers-diet-cycle.png

This forms the feedback loop you need to lose weight. By going through multiple iterations of measurement and adjustment, it is simple to reach your goal.

Getting Ready

If you have little knowledge of calorie content of foods, and tracking weight is new to you, it may be wise to spend a couple of weeks just getting used to the actions — monitoring your daily weight and measuring your calorie spend. Once you’ve become accustomed to your weight fluctuations and the procedures, you’ll be better equipped to execute your plan.

When you’re ready to start, follow these steps:

1) Measure your current weight and set your weight target. A general weight goal is to set your target weight based on your height and your frame

2) Figure out your desired deadline for reaching your target weight. Get the number of days between today and your deadline.

3) Calculate your calorie deficit. This is given by the simple formula:

(Target weight loss in pounds) * 3500 / (Days to deadline)

For example, if you want to lose 10 pounds in 2 months (or 60 days), you will need to run a deficit of (10 * 3500 / 60) = 583 calories per day.

As a rule of thumb, 500 per day loses 1 pound per week. Cutting more than 500 calories per day is difficult, and more than 800 calories very difficult to sustain. It’s better to have a more conservative target first then ramp up your deficit as you get more experience, rather than setting an impossibly difficult target upfront and giving up the whole endeavor.

4) Finally, take a few before pictures of yourself. Ideally get a full-length picture of your front, profile, and back. Do this in a mirror or ask someone to take them for you. While you may be hesitant to do this, it has a number of benefits:

The Initial Plunge

The first 3 days are the hardest. It gets easier. Know this, because otherwise you’ll think you need to endure weeks of the same magnitude of pain.

In your normal diet, your body is used to a bounty of plenty. It just burns whatever you eat, and stores the excess. Life is good. When you have a calorie deficit, your body burns all that you eat, and it burns fat to make up the shortfall. But switching from fat storage to fat burning takes time — around 3 days.

In the first few days, your body will panic from the sudden deprivation of calories. Dieting, after all, is just a euphemism for “deliberate starvation.” Your body will shut things down to conserve energy. At this point, you’ll experience the most severe shortage of nutrition in the entire course of the diet. You’ll feel cold, weak, irritable, tired, and a constant gnawing hunger. It is this bad, and it’s not good to sugarcoat this — better for you to know what will come and handle it better.

But your body is also smart, and it quickly adapts to what it perceives as the “new normal.” Your body won’t let you be weak, irritable, and starving for months on end. It switches from metabolizing food you eat and storing fat, to fat burning. But it takes some time for this to kick in. Once you pass the first 72 hours, the worst is behind you. It’s unlikely you’ll experience anything as bad as the first days. Knowing that an unpleasant experience is limited in time will get you through it.

The pain is an investment for a lifetime of reduced suffering. Endure 3 days of hunger on one side, vs 8 months of recuperation from a heart attack on the other. Furthermore, any pain that you feel now should be motivation for you to keep your weight, so that you’ll never have to go through that again.

If you’re having trouble getting past the first few days, the author suggests an alternative of partial fasting in the first few days of dieting, ingesting only about 500 calories a day. He suggests a more extreme calorie deficit hastens the transition time to burning fat, so adaptation might happen in 2 days instead of 3. Further, the pain of being 1200 calories short might not be perceived as much worse than 500 calories a day. If you do this, drink plenty of liquids since this makes you feel more full.

When and How to Start

Start your weight loss during a regular period of time when you have a regular schedule, ideally of at least 2 weeks of “normal life.” Maintaining a weight loss plan benefits from momentum and “getting in the groove.” During a vacation, extensive travel, or holidays, it’s hard to maintain the discipline your plan requires.

Start your diet at the beginning of a work week, typically Monday. Work is a useful distraction from hunger. Otherwise on weekends, if you just sit around hungry, you’re likely to break your calorie limit. If you start on Monday, by the time Saturday comes, you’ll be well adapted and past the 72 hour hump.

Before you start, sit down and plan out the first five days’ meal plan. Include specific foods at specific times. Having this certainty will help you deal with hunger by knowing that the hunger time is limited. It’ll also help you avoid the temptation of preparing more food or eating more when you’re hungry.

The Long Haul

Past the first 3 days, and past a few weeks, you’ll find that the diet becomes less of a bother. The hunger softens from an aching pain you think about constantly, to a minor annoyance that becomes a fact of life. And the positives will start arriving — you’ll notice changes in how you look and feel, and the rewards will motivate you to continue.

Continue tracking your weight daily and computing the trend. Don’t make sudden adjustments to your plan. Reflect every 3 weeks or so. And if you do make a change, don’t expect to see the change reflected immediately in the trend line — it lags behind, and will take at least 1-2 weeks to show up.

Troubleshooting

Day-to-Day Fluctuations in Weight

Don’t use your day to day weight as the number you derive self-worth from. As you know, it is almost entirely water influenced by salt. Focus on the trend line. As long as the trend is going down, ignore your daily weight. This means not being disappointed by sudden gains of weight, while also not getting excited about sudden drops of weight.

Plateaus in Weight Loss

You may notice periods when the trend line stalls for a few days. You might be getting through a stable point for your body. Stay with the diet and in a few more days the trend will resume its decline.

Drink Liquids

Drink at least 2 quarts of liquid daily. An easy way to do this is to measure it out in a container, and make sure you drink it by the end of the day. This will help you feel less hungry by filling your stomach, and it’ll also flush out metabolites from your new fat burning.

Constipation and Stool

Your body is used to moving a certain volume of food through your digestive tract a day. When you reduce the volume of food you eat, you absorb a greater percentage of the food you eat, and there is less bulk to move the stool through.

Eating lots of fiber and vegetables is the best way to deal with this.

Side Effects of Weight Loss

By far, the benefits of weight loss outweigh any of the downsides. But there are a few downsides:

Overall these are mild, temporary downsides during the course of calorie deficit. When you reach your target and resume maintenance calories, your body will adapt again and life will be good.

Lack of Social Recognition of Weight Loss

“Why is no one noticing my weight loss? I wish someone would compliment me.”

Don’t blame people. First off, it’s hard to perceive day to day differences, especially through just your face and your hands, which is typically all that they see of your body.

What will happen is one day someone will say, “hey didn’t you use to be fat?”

In any case, don’t strive for feedback from others — get validation from your weight tracking.

Secondly, many people may actually suspect you’ve lost weight, but out of politeness keep they it to themselves. Imagine if you thought someone lost weight, you asked if they had, and they said, “no” quietly and disappointedly. People want to avoid this awkward situation.

Dealing with Hard Times and Hunger

There will be bad days. Your boss yelled at you, your parents don’t like something you’re doing, your car breaks down — all at once. With all these stressors, it’s hard to stay on goal and not cheat on your diet, going back to your favorite foods.

The worst setbacks often happen late at night. Hours after you eat dinner, you’re hungry again. You’re alone, so no one can help you. You may be around food around the house, so a snack is tempting.

In these times, remember why you’re doing this. You may want to live longer; have better health; avoid terrible complications like heart attacks; accomplish more in life and career; get more social acceptance.

Also, think about why you eat. Are you eating because you want to eat, or are you eating to stop the hunger? Be very careful about this distinction. More often than you think, we eat as a ritual, to stave off boredom, or from social pressure.

Also, think about how you’ll feel after cheating your meal plan. Guilty? Disappointed? Protect your future self from shame by making the strong decision today.

Finally, if you have a predictable time of day when you’re hungry, consider shifting some calories to that time.

Success and Transitioning to Stability

Eventually, your weight will hit your goal. Congratulations! But don’t let off immediately. You need to transition from losing weight to maintaining weight stability.

First, even if you weigh under your target, give yourself a little margin of safety.

When you hit these goals, next, don’t immediately add your calorie deficit to your current meal plan. Your body has become more efficient at using limited calories — it’s ramped down your metabolism — and it needs to shift back to burning your food. Transition back over 4 weeks by adding back a quarter of the calorie deficit week by week.

Allow some time for settling. If the trend line is bumping up, then cut back again by a quarter of the calories, then let things stabilize.

Then that’s it. Your diet is finished. Your weight problem is history. The discomfort is over. Next, we’ll cover how to guarantee you’ll never gain back the weight you just lost.

6: Perfect Weight Forever

The majority of people who lose weight end up gaining back every pound they lost. You might have gone through a few cycles of this yourself. You might feel hopeless that even if you do lose weight, you will inevitably gain it back — so what’s the point?

The reason people regain weight is that they don’t change their eating behaviors after they lose weight. Meeting their goal, they blissfully return to using their broken eat clock.

Assuming that you were born with a broken eat clock and it’s not possible to develop a working one, keeping your weight for a lifetime requires a lifetime of guidance about how much to eat. Specifically, this means continuing the best practices of what got you here: 1) daily weight tracking and 2) meal planning.

Someone with poor eyesight has to wear corrective lenses to see properly. Without them, she is lost. Likewise, you may have to accept that you have genetically problematic eating controls.

This is the cost of being healthy and avoiding yo-yo weight fluctuations. It’s also the cost of earning valuable freedom — in the foods you eat, your meal schedule, and how much or little you exercise. You can return to eating whatever you want — just in limited, predetermined portions.

Remember the pain you felt during your weight loss. You don’t want to go through that again, do you? Look back at your starting photo. You don’t want to look like that again, do you? It’s worth it.

Note this does NOT mean being on a diet for the rest of your life. It simply means eating at maintenance calories forever. You can still enjoy all the foods you like — just in moderation.

But if you’ve failed before, why will you succeed this time? After reading this, you now understand your body and weight to a degree you never had before. You’ve devised your own successful diet plan. You’ve stabilized your weight, rather than yo-yoing back into bad habits.

Daily Weight Tracking

Once you reach your target weight, you must not lose discipline in tracking your weight daily. Day to day variations are hard to detect in the mirror. Without measuring yourself, you can gain 5 pounds within weeks, with the only warning sign being your clothes one day fitting less well. By then you have to endure the painful transition to calorie deficit once again.

The goal is to keep tight thresholds around your target weight. If you go overweight and break a threshold, you have to modify your behavior to lose the weight again.

(The above is written assuming you’ve gained weight, since this is by far the more common problem, but the same applies to unexpectedly losing weight. If you’re losing more weight than you want, then you need to increase the number of calories you eat.)

The idea is a negative feedback loop, where perturbations from your target weight are nudged back toward your target weight.

Luckily, as you master controlling what you eat, the instances where you hit the brick wall become rarer.

Meal Planning

Once you reach your target weight, you have the benefit of increasing your daily calorie intake to your maintenance amount. If you were cutting at a rate of 500 calories per day, then you get to add those calories back to your diet.

However, you must not lose discipline around planning your daily calorie intake and planning your meals. If you return to your previous eating habits (eating more than you burn), you will inevitably gain weight.

Even if you control yourself to a large extent, slipping just a little bit each day will still cause your weight to creep up. An extra 200 calories per day — just a handful of nuts, a second serving of mashed potatoes — means you’ll gain 1 pound roughly every 2 weeks. At the end of a year, you’ll have gained 20 pounds.

These insidious small doses of eating lead to feelings of futility and helplessness. “I didn’t even change anything — I haven’t gone back to my all-out binges, but I still gained weight.” Sticking to your meal plan will prevent this setback.

Luckily, over months, you will develop a good intuition for how many calories a type of food contains. You develop a habit of eating a reasonable amount at a meal, and exceeding this feels inappropriate. You’re still planning meals, but doing it subconsciously, in your head. You know that a dollop of mashed potatoes, with two chicken drumsticks, is the right meal size.

Keeping Weight

If you follow both strategies, you’ll stay thin for the rest of your life. Others will ask, “how do you manage to stay so thin?” The answer: “When I start to gain, I eat a little less. When I start to lose, I eat a little more.” Simple. And maybe a little easy, once you learn to do it.

Finally, even though you’ve fixed your own weight problem, many still struggle with theirs. Don’t have contempt for those who haven’t achieved enlightenment like you have; also don’t nag them to emulate your practices and convince them to adopt your ways. Your success is the strongest form of persuasion. When they are ready to receive help and when they approach you, only then should you share what you’ve learned.

7: On Exercise

The most important thing to understand about exercise is that diet control is far more effective at causing weight loss than exercise. For most people, it is much more painful to burn 100 extra calories by jogging than it is to merely avoid 100 calories of food.

But what about gaining muscle? Each additional pound of muscle only burns 6 calories per day. And gaining a pound of muscle is far harder than you think.

This is not to say that exercise isn’t beneficial. The medical consensus is that exercise is great for overall health outcomes, quality of life, bone density, energy levels, sleep quality, etc. But merely for the purpose of losing weight, you should focus on meal planning and calorie cutting, rather than burning more calories through exercise.

The book has a chapter on exercise, mainly around body weight fitness (pushups, squats, running in place, and leg lifts). The author suggests tracking your progression on these exercises, as a way of motivating yourself and seeing how you’re getting more fit as you lose weight. Since exercise is a far-reaching topic, we’re choosing not to summarize more here, but you can read the original chapter here.

Exercise: Reflecting on Weight Loss

Think about what you’ve learned from this book and how you’ll approach weight loss now.