At some point in our lives, we’ve all heard the calories in/calories out approach to weight loss and body composition. As the theory goes, provided you’re eating fewer calories than you burn in a given day (or working harder to burn more than you take in), you’ll stay trim. Gaining weight, therefore, is typically result of either eating too much (Taubes refers to this as “gluttony”) or moving too little (referred to as “sloth”).
In Why We Get Fat, author Gary Taubes argues for a different approach. What if gluttony and sloth aren’t the cause of why we get fat, but the result of getting fatter?
When a child grows, we don’t say that she’s growing because she’s eating so much during her growth spurt. We say that she’s eating more because she’s in a growth spurt. Hormones that encourage growth are the cause; eating more calories to sustain that growth is the consequence.
Taubes makes the case that getting fat works the same way. Fat accumulation has more to do with hormones (namely, insulin). At improper levels, these hormones create an environment that’s conducive to fat storage; our bodies essentially become experts at storing fat. This same fat storing environment leads to increased hunger and decreased activity. They’re the effect, not the cause, of getting fat.
I recently listened to the audiobook and found it pretty eye-opening. I thought I would share some of my main takeaways here, but I encourage you to get the book if you want a full deep dive!
Debunking Calories In/Calories Out
The calories in/calories out theory has reigned supreme over diet advice for years. When I studied exercise science in school and went through personal training certifications, it was the overarching theme for how to guide someone to weight loss – have them eat fewer calories than they expend. In Why We Get Fat, Taubes provides a helpful analogy that explains where this theory falls short.
Let’s assume that you own a movie theater. You open your doors to the public, and you’re thrilled to find that crowds are rushing in throughout the day to see movies at your establishment. In fact, more people are coming in every hour than are leaving. As a result, your movie theater becomes more and more crowded.
You might ask your general manager, “Why is it so crowded in here?” That general manager might respond, “Well, it’s more crowded in here because more people are coming in than are leaving.” That answer wouldn’t actually address your question though, right? It’s a given that more people have to come in than leave in order for the theater to get crowded. You care more about why. Why are more people coming in than leaving?
This same logic applies to calories in/calories out. Saying that we get fat because we bring in more energy than we expend doesn’t help us to answer the fundamental question. Why are we bringing in more energy than we expend? What’s the cause?
Taubes goes on to further back up his claim that calories in/calories out is too simplistic citing many studies and historical examples of societies in poverty that had low food availability yet suffered high obesity rates. Perhaps the most compelling piece of evidence in my mind though was a set of two experiments done on rats.
Two Experiments. One Simple Takeaway.
In the first experiment, researchers removed the ovaries from a set of rats. Then, they sat back and watched what happened to their eating behavior and weight. According to Taubes, “The rats would begin to eat veraciously and quickly become obese.” This matches our expectation with calories in/calories out. The rats became obese because they ate too much. Simple as that.
In the second experiment though, researchers again removed the ovaries from another set of rats. However, the rats were put on a strict post-surgical diet. Even if they wanted to overeat, they couldn’t satisfy that urge. We should expect these rats to remain lean, correct?
Wrong. The rats got just as fat, just as quickly, but these rats were completely sedentary.
Taubes summarizes the results like this:
The animal doesn’t get fat because it overeats, it overeats because it’s getting fat. The animal is unable to regulate its fat tissue…Removing the ovaries from a rat literally makes it’s fat tissue absorb calories from the circulation and expand with fat. If the animal can eat more to compensate for the calories that are now being stashed away as fat (the first experiment), it will. If it can’t (the second), then it expends less energy because it now has fewer calories available to expend.
All About Insulin
If calories in/calories out isn’t the answer, what is? Taubes argues that the real answer to why we get fat lies in the enzymes and hormones that regulate our fat cells. He focuses on one hormone in particular – insulin.
You likely recognize insulin as the hormone that regulates blood sugar. When we eat a meal, insulin is released to pull the sugars from our blood stream and distribute them around the body. Meals high in carbohydrates (aka sugars) cause the body to release higher amounts of insulin in the blood.
It turns out that insulin also has a large impact on the regulation of our fat cells. It does this in two primary ways according to Taubes:
- High levels of insulin in the blood discourage fat from being burned as fuel by muscle cells. To the contrary, insulin actually encourages fat to be stored in our fat cells. In short, it creates a fat-loving environment.
- Insulin also suppresses the activity of HSL (hormone-sensitive lipase). Long, science-y name – all you need to know is HSL works inside the fat cells in our bodies to break down triglycerides so they can be used for fuel. HSL makes us leaner. By suppressing HSL, insulin, again, works to make us fatter.
This is obviously a bit simplistic, and Taubes goes into far greater detail in Why We Get Fat, but this line sums it all up pretty nicely:
The bottom line is something that’s been known and ignored for almost 40 years the one thing we absolutely have to do if we want to get leaner if we want to get fat out of our fat tissue and burn it, is to lower our insulin levels and to secrete less insulin to begin with.
What Should We Do Next?
Taubes’ suggestion to “lower insulin levels and secrete less insulin to begin with” sounds great on paper, but what should we do on a day-to-day basis to actually put this into practice? Two suggestions:
- Eat fewer carbs especially easily digestible ones like breads, cereals, potatoes, soda, etc. “These foods flood the bloodstream quickly with glucose. Blood sugar shoots up; insulin shoots up; We get fatter,” according to Taubes.
- Get in the gym for some intense exercise. Exercise has a positive impact on insulin sensitivity. With an increased sensitivity to insulin, we can get by with secreting less insulin after meals leading to lower levels of insulin overall (and we get all the good endorphins associated with exercise). Win win win!
If you’re hungry for more, I would encourage you to read Why We Get Fat and check out the following resources:
- Nutrition Brief: Insulin and Blood Sugar Regulation on the CrossFit Journal
- The Science of Obesity on Farnam Street
- Finally, watch this video by Taubes for a good summary:
The last thing I’ll leave you with is the nutritional recommendations from CrossFit, which fit Taubes’ recommendations really well!
Eat meat and vegetables, nuts and seeds, some fruit, little starch and no sugar. Keep intake to levels that will support exercise but not body fat…