Why dieting sucks for your metabolism

Flourish’s approach to nutrition stems from the desire many women have to escape from the endless cycle of dieting. You diet, you make progress toward your goal, and then it becomes unsustainable, you “cheat” on the diet, and that progress is reversed. We’ve all been there—probably more than once. Flourish wants to help women break that cycle with a better understanding of their bodies and their health. Most importantly, Flourish is here to help you understand that weight doesn’t determine your health and that building healthy, long-term habits will outlast any fad diet.

Take a moment to think back on your diet history…

What was the first diet you went on? How old were you? Why did you go on it in the first place? What results did you get? Did they last? How has your diet history progressed from there?

Diets promise to make you healthier and happier by slimming you down. But the research shows that diets consistently fail. In fact, most dieters will go on to regain more weight than they initially lost.

What’s wrong with diets?

Weight loss, gain, and maintenance is more than just calories-in vs. calories-out. Bodyweight is determined by a complex neuro-hormonal system that's impacted by genetics, environment, behavior, and more.

That system has checks and balances in place that will reverse weight loss quickly on a diet, returning to the original weight or higher. Your body doesn’t hate you. It just wants to survive.

How many times have you lost and gained the same weight? Have you noticed that sometimes the longer you diet, the more your weight increases? Following the quick weight loss tricks that got you into your sorority formal dress might feel like a Herculean task now, and they don’t even yield the same results. What’s up with that?

The diet industry likes to claim it’s your lack of self-control or insufficient willpower. But that’s not true—none of what you’re experiencing is your fault. You’re not failing the diets, the diets are failing you.

What is metabolism?

Weight management is often boiled down to the simple calories in vs. calories-out equation. Admittedly, this isn’t complete BS. Without underlying issues or imbalances and within a reasonable lifestyle, weight is gained in a caloric surplus and lost in a caloric deficit. But it is a vast oversimplification.

Your metabolism is basically the total of all systems in your body using and expending energy. Energy almost always comes from food, as our bodies can’t actually create our own sources of energy. Your body wants homeostasis; it wants energy in to equal energy out.

Total daily energy expenditure (TDEE) is a combination of four factors. Resting metabolic rate (RMR) is the energy required by your body at rest over a 24 hour period. The thermic effect of feeding (TEF) is the energy it takes to digest, metabolize, and absorb food. Exercise energy expenditure (EEE) is an easy one. Non-exercise activity thermogenesis (NEAT) is the energy you burn doing all your normal activities like brushing your teeth or cooking dinner.

RMR contributes the most to TDEE, and TEF the least, but TDEE is the total amount of all these processes together.

So when people say calories in = calories out, that really means:

Energy from food = TDEE, which actually means:

Energy from food = RMR + TEF + EEE + NEAT

It’s not very simple at all.

What happens to your metabolism on a diet?

On a diet, the “calories in” side of the equation decreases, because you’re taking in less food. Sadly, the beauty standards of the past 150 years haven’t managed to overcome the processes we’ve evolved over the last five million years or so. Your body can’t tell why you’re cutting calories. All it knows is that it’s taking in less food. Evolutionarily speaking, that generally meant famine or inadequate access to food. Your body now focuses on survival, and will seek energy balance above all else.

Basically, your body will make sure it’s adjusting “calories out” to match the dip in “calories in” as time continues in an effort to keep you alive. Because both sides of the equation are decreasing, and your metabolism is the total of all the processes regulating energy in your body, your metabolism slows on a diet. And thanks to a phenomenon called adaptive thermogenesis, it will actually fall more than you'd expect based on body composition or decreased TEF.

But there are actually even more processes involved in metabolism and dieting than just this calorie expenditure equation.

What do hormones have to do with metabolism?

Hormones are one of the major factors involved in metabolism besides the energy expenditure equation. Many hormones are involved in your consumption and utilization of food—things you know, like insulin, and things you’ve probably never heard of, like ghrelin, gastric inhibitory peptide, leptin, PYY, and CCK.

For now, we’ll focus on leptin and ghrelin, and how that drop in “calories in” can cause other negative side effects in your body.

Leptin is a hormone, released by fat cells, that gives you that feeling of satisfaction when you eat. Leptin is released in proportion to how much food you consume, so the less food you eat, the less leptin is released. The harder you diet, the less satisfied you feel.

Then there’s ghrelin, which many call the “hunger hormone”. Ghrelin regulates when you feel hungry, and taking in food lowers the levels of ghrelin in the body. So, unlike leptin, ghrelin is inversely related to food: the less you eat, the more ghrelin your body releases. When you restrict calories, your ghrelin levels increase, and you feel hungrier.

So why are diets so bad for your metabolism?

Dieting is, at its simplest, restricting calories. The “calories in” side of the energy balance equation is down. So your body kickstarts a bunch of processes to achieve energy balance.

Your resting metabolic rate will slow. Your TEF drops because you’re consuming fewer calories. You might not realize it, but your body will eventually become more sedentary, in turn reducing your NEAT.

Your leptin levels fall, so you feel less satisfied after you eat. At the same time, your ghrelin levels increase, so you’re feeling more hungry. Dieting is actually a stressor on the body—cortisol, the hormone that regulates stress, rises, which will increase carbohydrate cravings.

This is all happening in your body, but your mind is hard at work as well. It’s trying to restore energy balance as the quantity and intensity of food-related thoughts start to spike.

All of this was super helpful as we evolved and needed to survive amid less access to food and less shelter from predators. But in most of our lives today, we don’t need to worry about those things. It can be really frustrating to be at the mercy of evolution.

There’s got to be a better way...right?

Bottom line, you deserve to feel comfortable in your body. You deserve stellar health that fuels the life you desire. Diets position themselves as a quick fix to give you all of this, but your body has developed specific processes to perform this function. It’s a high-performance machine. It just needs you to give it the right fuel.