Diet, lose weight, regain weight, repeat, repeat, repeat. Yo-yo dieting is an all-too-common phenomenon. More and more people are dieting — whether for weight loss or for “health” — even though most do not maintain their weight losses.
This is unfortunate, because not only can yo-yo dieting lead to greater weight gain over time, but it may also put us in the path of heart disease and diabetes.
Even among people who lose a significant amount of weight — at least 10 percent — roughly eight in 10 will regain that weight within a year. But dieting and yo-yo dieting are not limited to people at higher weights. While National Health and Nutrition Examination Survey data show that the percentage of dieters who weigh in the normal range on the body mass index (BMI) chart is on the rise — currently almost 50 percent of women and 20 percent of men — more than 10 percent of women with an underweight BMI reported that they want to lose weight. Many adults, adolescents and children with normal or low BMIs diet because they feel pressure to be thinner.
Some of that external pressure may come from public health messages. “Terms like ‘war on obesity’ and obsession about slimness can backfire over the long term,” said Abdul Dulloo, professor in the department of medicine and psychology at the University of Fribourg in Switzerland. “The emphasis should not be about ‘body weight’ or ‘body fat’ per se, but about motivation for a healthy lifestyle in relation to food and physical activity.”
FEAST OR FAMINE
The very act of weight loss — especially the loss of muscle that accompanies all weight loss — triggers the body to fight back by increasing hunger, slowing metabolism and encouraging fat storage. This metabolic adaptation served our ancestors well during feast and famine, but not so much in today’s food environment, which encourages weight gain in people who are genetically predisposed to it. Repeated dieting attempts do nothing to reduce this vulnerability. Restricting food increases its appeal, which can lead to overeating, or even bingeing, and then weight regained.
Instead, what happens is fat “overshooting” — regaining more fat than was originally lost. The body wants to regain lost muscle, but regains fat first, so the drive to eat and slowed metabolism continue until muscle regain is complete. Overshooting after each cycle of weight loss and regain can contribute to an overall increase in weight over time.
A recently published study in the journal Evolution, Medicine, and Public Health proposes that the body’s uncertainty about food supply — and the body can’t tell the difference between intentional dieting and unintentional famine — may cause it to store more fat each time food restrictions are lifted than it would if intake remained steady.
What’s more, yo-yo dieting in people who have BMIs at or below the normal range appears to increase risk of Type 2 diabetes, high blood pressure and heart disease. What about people who start dieting at a higher body weight? Research is inconclusive, in part because of varying definitions of yo-yo dieting used in studies. Some dieters may have one large loss and regain, while others may experience several smaller loss-regain cycles.