69 percent of Americans over the age of 20 are either overweight or obese, according to the Centers for Disease Control and Prevention (CDC). And a 2010 University of California Los Angeles (UCLA) study showed that at any given time about 47 percent of U.S. adults are trying to lose weight, sometimes in multiple attempts. What happens? Why do weight loss diets not work?
There is a huge amount of research showing that most weight-loss diets, which typically restrict calories and/or increase activity, succeed short-term and fail long-term, when the weight is regained. Much of this research points at reasons that have been hard-wired into human brains for thousands of years.
Neuroscientist Sandra Aamodt says the brain makes us eat and build energy reserves when food is available. Since humans have historically had to deal with food shortages and famines the body has learned to store those reserves, even though most Americans no longer have to deal with the threat of starvation. She says thinner people burn fewer calories because of the brain’s message to hold onto the weight.
According to Aamodt, diets are dysfunctional because the human brain is set to keep us at the weight it says is appropriate, even if a different body size is desired. We diet, get hungry, overeat, make poor eating choices, and then gain back the weight and feel miserable. Dieters may think they always need to avoid food, which is tough to do because we have to eat to live. Stress results, and other studies have linked stress to weight gain.
The UCLA study “Low-Calorie Dieting Increases Cortisol,” published in the journal Psychosomatic Medicine in May 2010, followed the dieting habits of 115 female participants. A. Janet Tomiyama, PhD and lead study author, says that weight-loss diets most commonly reduce the number of calories consumed, but this type of weight loss is short-term, resulting in 30 to 64 percent of dieters gaining back more weight than they lost.
Tomiyama says that calorie-restricted diets create mental and physical stress and lead to increased production of the stress hormone cortisol, which is linked to an increase in belly fat. The study says that calorie-restricted diets are the weight-loss option for most people, but that it does not work, in part due to potential physical and mental harm.
A great deal of research (as well as anecdotal evidence) shows that most calorie-restrictive diets succeed short-term, but fail long-term. In 1991, Garner & Wooley showed that there was virtually no evidence that clinically significant weight loss can be maintained long-term through dieting by most people. And in 2013, Sumithran & Proietto found that dietary restriction and/or increased physical activity can usually result in weight loss, which the majority of people regain long-term.
A frequent assumption by the general public is that weight-loss diets fail due to weak willpower, moral failure, laziness, or gluttony. Many people believe that weight is a product of moral character and effort, and is entirely a choice. These explanations are not supported by scientific literature. Here are some theories about why diets fail:
Behavioral relapses and going off the diet may be due to hunger, negative moods, emotional stress, and social pressures. The obvious reason for regaining weight is the return to inappropriate eating and exercise habits.
Lowered energy expenditures, because as people get thinner they use less energy just to exist. Less energy is required to maintain a smaller body.
Fat storage and insulin sensitivity are altered during dieting. When cells are resistant to insulin, glucose cannot get into cells, so they switch to fat burning. During weight loss, cells become more sensitive to insulin, which lets more glucose into the cells. This glucose gets used for creating energy instead of fat. The fat gets stored.
Increased appetite, as the levels of hormones involved in appetite control change during and after weight loss. The hormones that provide the feeling of fullness decrease with weight loss, and the ones that stimulate hunger increase.
Genetic tendency to gain weight.
British psychoanalyst Susie Orbach says that if dieters respond to natural hunger they will reach a healthy weight. Unless, of course, they have dieted for so long that they no longer recognize natural hunger. Diets may contribute to fat storage and compulsive eating, because deprivation inevitably leads to rebellion. Orbach says compulsive eating is eating according to a set of rule that get broken, but not in response to hunger.
Some people who try hard to stick with a weight-loss diet but find it is not working may be sabotaging themselves by eating the wrong foods. Authority Nutrition has a list of the top 11 diet foods that make people fat, even though they sound healthy. These include breakfast cereals, agave nectar, whole wheat bread, granola, low-fat yogurt, salad dressings, fruit juice, diet soft drinks, organic food that is highly processed, trail mix, and gluten-free junk food.
Some of these foods, like granola and trail mix, are calorie dense and may contain excessive amounts of sugars and fats. Others, like low-fat yogurt, have been extensively processed to get the fat out, but the fat has been replaced with unhealthy ingredients such as sugar. A 2010 study in the American Journal of Clinical Nutrition concluded that there was no evidence that saturated fat leads to coronary heart disease or cardiovascular disease. So in low-fat options such as yogurt, the good ingredients were removed and replaced with bad ingredients.
But all this evidence is no reason to give up on “dieting.” Tomiyama says people trying to lose weight should not give up on portion control or taking care about the type of food eaten. However, they should concentrate more on making healthy food choices and eating a balanced, healthy diet. She says not to use these results as an excuse to abandon weight-control efforts.
Aamodt says the key to weight loss is focusing on an overall healthy lifestyle that includes activity, exercise, healthy habits and mindful eating. Eat when hungry, stop when full. Neglecting to follow these essential rules is the key reason why weight-loss diets do not work.
By Beth A. Balen