Trigger warning: This post includes content related to eating disorders. If you are struggling with an eating disorder, please reach out to the National Eating Disorders Association (NEDA) Helpline: (800) 931-2237.

Dieting is not an effective way to lose weight, improve health, or become happy.

Diets Do NOT Work

Part I: Biology

For the purpose of this post, I am defining “diet” as eating restrictively (amount and/or type of food) for reducing one’s weight.

Dieting is not an effective way to lose weight, improve health, or become happy. In fact, most people regain all the weight that they lose on their diet within five years, and one to two-thirds of those people gain even more weight than they lost. This is not because they gave up on their diet or did not have enough willpower. Rather, it is because bodies have powerful biological and psychological responses to restrictive eating to keep them at a weight that is healthy for the person – a weight within their set-point range. In this post, I will focus on the biological responses to deprivation, but keep in mind that perceived deprivation/mental restriction, which I will talk about in an upcoming post, is just as powerful.

Diets generally result in weight-cycling (aka yo-yo dieting) or disordered eating/eating disorders. Both of these outcomes are far less healthy than living in a larger body and have far more severe health consequences. Most people who diet experience weight cycling. So I will address that first.

Our bodies want us to survive. Diets make our bodies believe that we are starving, and our bodies will do everything that they can to support our weight. If we diet enough, our bodies predict future famine and increase the weight they want to maintain with fear of future weight loss.

Set Point Theory

Our weights, like our heights, are mostly determined by our biology–not our behaviors. Yes, if you eat nutritiously as a child, you might grow to be slightly taller than if you didn’t. However, if your parents and grandparents are short, it is unlikely that any amount of nutrition will allow you to grow as tall as your friend with a tall family. Likewise, no amount of dieting and exercise can make a fat person thin. You do not need to take my word on it; just look to science. There is no scientific evidence supporting the idea that any diet promotes long-term weight loss or health promotion.

Our set point ranges are the biologically determined weights that our bodies want to support. These are the weights at which our bodies are the healthiest and at which we physically feel our best and our bodies are functioning optimally. If we diet and our weights drop below our set point ranges, our brains (specifically the hypothalamus) send signals to our bodies to release hormones, enzymes, and other chemicals to bring us back to weights that are right for us. (Note: This weight is likely far higher than our society and media lead us to believe.) According to scholar and Health at Every Size activist, Linda Bacon, “If you’re losing weight and you are below your set point, your hypothalamus might direct other body systems to regulate your eating and activity levels as well as your metabolic efficiency, the rate at which you burn calories, to get you to regain the weight.” (Health at Every Size, p. 15)

The Biological Response to Diets:

Leptin, Insulin, PYY, and Ghrelin

The hypothalamus regulates your body systems to maintain your set point range partly by releasing hormones, enzymes, and chemicals that are strong biological forces to help you reach your set point range. For example, if your brain is perceiving famine, it will increase your appetite, alter how you experience the taste of food, drive you to crave foods that are high in fat, lead you to decrease your physical activity, make you feel cold to reduce energy expenditure, and even lower your metabolic rate.

One protein that contributes to your set point range weight maintenance is leptin. According to Linda Bacon, your body fat sends leptin “to the brain where it triggers the release of various chemicals to turn down your appetite, speed up your metabolism, and get you moving more” (Health at Every Size, p. 21). Conversely, when you are dieting, leptin protects you from weight loss. As you lose body fat, your leptin production decreases. Thus, your appetite increases, your metabolism slows down, and you move less. Leptin reduces hunger; weight loss reduces leptin. Insulin is a hormone that regulates blood sugar levels. PYY is a gut hormone that reduces hunger. Another hormone that contributes to the maintenance of your set point range is ghrelin. While leptin, insulin, and PYY reduce hunger, ghrelin increases hunger. These are just a few of the chemicals working to maintain your set point range. According to Linda Bacon, “More than twenty chemical messengers have been found to stimulate eating, and a similar number suppress appetite” (Health at Every Size, p. 23).

Thus, it is not your fault that you “failed” at your diet if you have gained weight in response to your diet. Your body has worked optimally to save you from starvation during a time of famine. Your body’s biological response to deprivation was successful. Evelyn Tribole and Elyse Resch explain, “While intense eating may feel out of control, and unnatural, it is a normal response to starving and dieting” (Intuitive Eating, p. 6).

While society wants us to lose weight, our bodies desperately want to maintain weight. And, our bodies feel safer gaining weight than losing it. Your body strongly protects you from going below your set point, but weight gain is easy. Thus, losing weight may increase your set point.

In review, dieting increases your appetite, suppresses your feeling of fullness, slows your metabolism (the rate at which you burn calories), causes cravings for foods that are high in fat, and increases the effectiveness of fat storage processes. It also leads to psychological effects, such as preoccupation with food, which I will discuss in a future post.

Eating Disorders

In addition to simply regaining the weight, dieting can lead to eating disorders, especially binge eating disorder.

Binge Eating Disorder (BED)

Remember, according to the National Eating Disorders Association, “A history of dieting and other weight-control methods is associated with the development of binge eating.” It is no wonder that BED is so prevalent in our society. Given the biological evidence above, it makes sense that so many people who diet to lose weight struggle with BED. (Check out my blog post, “What is an Eating Disorder?” for a refresher on the criteria for diagnosing BED.) Their diet deprives them of the nourishment that their body needs, so the brain sends hormones, chemicals, and enzymes throughout the body to reverse this deprivation by consuming a large amount of food quickly. Binge eating disorder is dangerous because it can lead to weight-cycling and weight stigma, which both have serious biological and psychological consequences (especially those improperly attributed to obesity).

If you developed BED and regained the weight that you lost dieting, try reframing your thoughts about your body. Can you thank your body for saving you from starvation and not shame it for its size?

Anorexia Nervosa

Some people do not “fail” in our diets. This occurs when there are flaws in the body’s biological survival mechanisms. We lose weight beyond our bodies’ healthy set point range, and our bodies fail to send chemicals to our brains to force us to eat more and move less. Our bodies begin to consume our own muscles and conserve energy by decreasing our ability to regulate our temperature. Eventually, if not treated, many people with anorexia eventually face very serious health outcomes that may result in electrolyte imbalances, cardiac arrest, and death. Anorexia nervosa has the highest mortality rate of all mental illnesses. Evolutionarily, we would not have survived times of famine. We do not “succeed” in our diets due to willpower; we “succeed” in our diets due to our bodies’ failure to respond appropriately to deprivation.

If you struggle with anorexia nervosa, you can thank your body, too. It tried to save you from a society that shames people in larger bodies. However, knowing that your body will not force you to eat more or move less, you need to consciously work even harder to take care of and nourish your body.

If you are struggling with an eating disorder, please reach out to the National Eating Disorders Association (NEDA) Helpline: (800) 931-2237.