Why We Get Fat

You might see this title and think, “we get fat when we eat too much and/or don’t move enough”, or “it’s thermodynamics – you don’t expend as much energy as you consume”. Although, I’m guessing most of you didn’t actually think of the term thermodynamics right away.

The title of this blog is the name of a book by Gary Taubes that I often find myself recommending to others. And, because many people don’t have the time or the inclination to read this book, I wanted to share the key messages.


First, his extensive research paints a very clear picture of how we are asking the wrong question about weight gain and weight loss.

Second, it makes a compelling case that the prevailing messages about managing weight are flawed.

Third, I’ve seen effects first-hand.

Why, Not How

If your first response to “why we get fat” is that we consume more energy than we expend, you are not answering the right question.

Consider the author’s example to illustrate this point. If you add more people to a room, it gets crowded. If you asked “why is this room crowded” and someone replied, “because more people entered than left”, that’s not very helpful and does not actually answer the question, which is why is the room crowded? Why are there more people in this room?

Switching back to the body, why is there extra fat (stored energy) on this body? Simply explaining how fat accumulates is not the answer to why fat accumulates.

It’s Not as Simple as Calories In/Calories Out

Perhaps you have tried reducing your calories or increasing your exercise as a means to lose extra weight. And maybe it worked for a while. Usually at the start, it does work. But many people eventually plateau and the same approach stops yielding results.

Take the example of the multi-year Women’s Health Initiative (WHI) that saw participants reduce their daily caloric intake by an average of 360 calories per day, yet after 8 years, the average weight loss was 2lbs along with increased abdominal fat.

Also, there are plenty of examples of populations around the world who are poor and underfed yet overweight. And these are not sedentary populations.

A great example of how the ‘calories in/calories out’ thinking is flawed is shown in the movie That Sugar Film by Australian filmmaker Damon Gameau (available on Netflix). Over 60 days, he consumed the average amount of added sugars that an adult consumes with a typical western diet – but – he kept his daily calories and daily exercise routine the same as before the experiment. Using the ‘calories in/calories out’ approach would mean he would see no change in his body composition. If a calorie is a calorie, then nothing should change. But boy, does his body ever change.

So What’s Going On?

A calorie is definitely NOT just a calorie. The foods we eat have different properties that we metabolize differently from one another. Proteins, carbohydrates and fats have unique structures that differently impact the hormones in our body that regulate our system and are responsible for using and storing energy.

What we eat is just as important as how much we eat. 

At the end of the day, what matters is our body’s hormones. When our hormones are out of balance or malfunctioning, there are all kinds of problems that can arise. And one of those problems is gaining and retaining fat. And until those hormones are balanced, it is a losing battle.

The worst part of this battle? When the prevailing idea is that you should just eat less or move more, it means you are just not trying hard enough.

We Have it Backwards

The current widespread message is that overweight or obese individuals eat too much and are sedentary. We assume these people have no willpower and are lazy.

Perhaps we need to flip this thinking.

Hormones are very powerful. In babies, hormones trigger feeding in order to grow and develop. As children grow, hormones signal consuming more in order to support development into adolescence and adulthood. During pregnancy, hormones drive a mother to consume enough for a growing fetus.

Or consider animals. Hibernating animals have hormones that signal to store extra energy leading up to the winter so they have fuel over the cold months, in which they also barely move to conserve precious energy.

Our bodies are amazing, and our hormones play a critical role.

And sometimes, our hormones are sending the message that fat should be stored and conserved AND energy should be conserved as well.

So maybe instead of overeating and laziness, we should consider that overweight individuals are being driven by our body chemistry to eat more (store more energy) and move less (conserve energy). If our body mistakenly thinks a long winter is coming, it’s going to get us ready for hibernation.

But we aren’t bears.

So Now What?

In the interest of this blog post not turning into a novel, I will write a follow-up post about the key hormone at play in storing and holding onto fat – insulin. It’s not the only one, but it has such a major role that it warrants its own post.

What I will say if you are someone confused about why you gain weight if you look at food while your friend can pack away a buffet dinner and never worry about not fitting into their pants the next day, take solace in knowing hormones are at play. And, that you can do something about it. Will you ever eat like your friend? Maybe not. But, you can take steps to regulate your hormones so they don’t work against you.