Diet, lose weight, regain weight, repeat, repeat, repeat. Yo-yo dieting is all too common. More and more are dieting - whether for weight loss or for "health" - even though most do not maintain their weight losses. Yet yo-yo dieting can not only lead to greater weight gain over time, but also may put us at risk for heart disease and diabetes.
Even among people who lose a significant amount of weight - 10 percent or more - about 8 in 10 will regain that weight within a year.
But dieting and yo-yo dieting are not limited to heavy people. The percentage of dieters who weigh in the normal range on the body mass index (BMI) is rising, now at almost 50 percent of women and 20 percent of men, according to data from the National Health and Nutrition Examination Survey.
And more than 10 percent of women with an underweight BMI say they want to lose weight. Many adults, adolescents and children with normal or underweight BMIs feel pressure to be thinner.
Some of that 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, Ph.D. professor in the Department of Medicine/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."
Weight loss - especially the inevitable loss of muscle - 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 it's not so great in today's food environment, which encourages weight gain in people genetically predisposed to it. Repeated dieting does nothing to reduce this vulnerability. Restricting food increases its appeal, which can lead to overeating, or even bingeing, and then weight regain.
What happens is fat overshooting - regaining more fat than was lost. The body wants to regain lost muscle, but it 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 increased weight over time.
Indeed, the body's uncertainty about food supply may cause it to store more fat each time food restrictions are lifted than it would if food intake remained steady, proposes a study in the journal Evolution, Medicine and Public Health.
Other research supports this idea. A 2015 article in the journal Obesity Reviews co-authored by Dulloo suggests lean dieters are at greater risk for fat overshooting than those classified as overweight or obese.
The lower a dieter's initial body fat percentage, the higher the proportion of muscle they lose and the proportion of fat they gain. Over time, with continued yo-yo dieting, this may substantially increase body fat.
Two studies of female twins in 2012 and 2013 found that the more frequent the cycles of yo-yo dieting, the greater the weight increase over time, especially among adolescents who start dieting at a lower BMI.
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.
Research for people who start dieting at a higher body weight 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.
"Weight for all bodies, fat thin, normal/high BMI, is not a thing that can be 'controlled' - it just can't," said dietitian Rebecca Scritchfield, author of "Body Kindness." "The only thing that can be controlled is choices, and you have to make choices that fit you best. Work on meaningful habits that you can change."
She suggests listing actions - or inactions - that disappoint you and framing your goals around new actions in line with the person you want to be. Not sleeping enough? Skipping workouts? Change that. Frustrated with how much alcohol you drink or how much you eat out? Change that, too.
"Even if these things don't lead to weight loss, if they make you happier they're worth it," she said. "You don't want the only reason you're taking on new health habits to be about weight loss. They'll never stick. Habits should be about joy, energy and other things that help you every day."