In Dr. Sandra Aamodt’s new book, Why Diets Make Us Fat: The Unintended Consequences of Our Obsession With Weight Loss, she discusses the neuroscience behind our repeated and unsuccessful diet attempts. Dr. Aamodt, a self-admitted, yo-yo dieter and neuroscientist, describes her personal history with weight cycling, binge eating, and obsessive dieting. She explains the science driving these behaviors and the reasons for our inevitable diet failures.
Short-Term Success, but Long-Term Failure
Diets may work in the short-term, but almost all diets fail in the long-term. Studies have shown that 80-100% of dieters who have successfully lost weight gain back the weight within a few years. This is in part due to the body’s drive to keep weight stable. Unfortunately, chronic dieting and weight cycling many times results in weight gain.
The Body Defends its Perceived Set Weight
The key concept outlined in her book is the idea that the brain defends the body’s perceived appropriate weight, called the set-point theory. The brain keeps body weight within a particular range, which Dr. Aamodt terms the “defended weight range”. The defended weight ranges between 10 to 15 pounds. The brain will always strive to keep weight within this range. Fluctuations can happen within the weight range and it is easier for weight to move up than down. If weight goes above or below the defended weight range, the brain will do everything possible to return to the body’s perceived appropriate weight.
The Struggle to Lose More Weight
To demonstrate why weight loss, or gain, within the defended weight range is possible, but weight loss below the range can seem nearly impossible, let's take an example of a 150-pound woman. Let’s say our 150-pound woman gains ten pounds over six months due to a busy period at work. Once the stressful work situation eases, she can lose those ten pounds by returning to her previous, regular eating habits and by making healthy food choices. If this same woman goes on a diet, restricting calories and increasing exercise, it’s very likely she could lose ten pounds and reach 140 pounds. Within the defended weight range, the body will adapt to these changes in weight loss or weight gain. But trying to lose more weight, to drop to 130 pounds, is more challenging.
If this same woman loses more weight to reach a 130-pound goal, the body will feel deprived, even starved. The brain will not adapt to this new weight, and instead, it will fight to return to the defended weight range, making further weight loss almost impossible and weight maintenance, at 130 pounds, incredibly challenging. Even small deviations from her diet will quickly result in weight gain.
The Brain’s Response to Starvation
It’s easier to understand the body’s desire to limit weight loss outside a set range if we think about it as a survival mechanism. Throughout human history, humans have had to endure periods of food scarcity, and we have survived many famines because of the body’s natural protective mechanism. When the brain perceives starvation, it immediately responds with the following:
• slowing down metabolism
• decreasing the drive to exercise
• increasing efficiency
• increasing hunger
These responses increase our desire to eat and limit our use of energy. This incredible mechanism has helped us survive famines and recover from periods of starvation. Unfortunately, this mechanism works against us in a world of food abundance. Our body’s natural drive to keep weight on, and to resist weight loss, has led to an epidemic of obesity and a nation full of obsessive dieters.
Effects of the Self-imposed Famine
Dr. Aamodt terms food restriction via dieting a "self-imposed famine" and states that this famine triggers the body’s survival mechanism. The brain perceives food restriction as starvation, particularly when the body is below the defended weight range, and it immediately attempts to protect itself. The body slows down metabolism, using as little energy as possible. Muscles become more efficient, capable of doing more work with less energy. The drive to eat is incredibly strong and hunger is intense. Dieting turns on the brain’s starvation mode.
Factors Contributing to Weight Gain and Weight Loss
Dr. Aamodt discusses other factors that contribute to weight gain, including environmental chemicals, sleep loss, stress, and social stigmas. She reviews the research and techniques for mindful eating (i.e.: the first bite will always taste better than the fifth bite) and mindless eating (i.e.: changing plate and glass size can help you unconsciously eat less).
Healthy is Better than Thin
After decades of dieting and weight cycling, Dr. Aamodt resolved not to diet for one year, to focus on healthy foods and exercise daily. She lost ten pounds. Pleased with the results, she now gives talks on diet avoidance and emphasizes a focus on health. She reviews research supporting her theory that being healthy, both with diet and lifestyle habits, but also by exercising daily, is more important than being thin. Adopting healthy eating habits and a healthy lifestyle will lower the risk of death from chronic disease in all individuals, regardless of weight.
Helpful Eating Tips and Strategies
Despite the dismal statistics on weight loss, Dr. Aamodt offers practical advice:
Two Dietary Goals
Two uncontroversial dietary goals:
1. Eat more whole vegetables
2. Minimize added sugar, refined grains and processed foods
If you are trying to lose weight, are a yo-yo dieter, have weight cycled over the years or have an interest in metabolism and energy balance, you will thoroughly enjoy the personal accounts by Dr. Aamodt as well as her explanation of the neuroscience surrounding weight loss.
Christine Dobrowolski is a nutritionist and whole-foods advocate.