The Truth About Losing Weight Through Diet Alone

This article is an excerpt from the Shortform book guide to "The Hacker's Diet" by John Walker. Shortform has the world's best summaries and analyses of books you should be reading.

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Do you need to exercise to lose weight? Is losing weight through diet alone possible?

According to John Walker, the author of The Hacker’s Diet, you can exercise for an hour and only burn 300 calories, but it only takes one Snicker’s bar to offset your workout. That’s why Walker suggests primarily relying on a calorie deficit to lose weight rather than on exercise.

Here’s why, when it comes to losing weight, diet outweighs exercise.

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. But losing weight through diet alone is actually more effective than exercise.

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: six Oreo cookies have 300 calories; a Snickers bar, 275 calories; medium fries at McDonald’s, 340 calories. Is it easier to not eat the 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. But don’t think that exercise can do the whole job. You’ll likely end up disappointed and abandon the whole program.

The Truth About Losing Weight Through Diet Alone

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Here's what you'll find in our full The Hacker's Diet summary :

  • An engineer’s approach to weight loss
  • Why losing weight is so hard even though it's so simple
  • What you have to do to maintain your ideal weight for the rest of your life

Hannah Aster

Hannah graduated summa cum laude with a degree in English and double minors in Professional Writing and Creative Writing. She grew up reading books like Harry Potter and His Dark Materials and has always carried a passion for fiction. However, Hannah transitioned to non-fiction writing when she started her travel website in 2018 and now enjoys sharing travel guides and trying to inspire others to see the world.

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