Are diets effective at reining in weight?
Most folks are at risk of regaining the pounds after 6 to 8 months
Dieting has long been viewed as the path to smaller bodies and better health. Stick to the right diet, the $75 billion U.S. weight loss industry may have you think, and you, too, can lose weight and keep it off.
The rise of weight loss drugs like Wegovy and Zepbound has highlighted just how ineffective dieting has been for the millions of people who have tried it. In a 2021 clinical trial of semaglutide (the active ingredient in Wegovy), for example, those taking the drug lost about 15% of their body weight in a little over a year, while those relying on just diet and exercise dropped only about 2%.
But there are many people who want to lose a few pounds for whom such medications are not the best choice. For those people, is old-fashioned dieting a good option?
We asked experts to help explain what dieting can — and can’t — do for you.
Can a diet help you lose weight?
In the short term, diets do seem to help most people lose at least a small amount of weight, whether it’s a low-fat or low-carb diet or calorie restriction, said Dr. Ellen Schur, the director of the University of Washington Nutrition and Obesity Research Center.
But results can vary. In one 2018 clinical trial, for example, researchers asked 600 people to follow either a low-fat or a low-carb diet for one year. While most participants lost weight — on average, 5% to 6% of their body weight (or 12 to 13 pounds) — about 15% gained weight during the study, and a only few lost as many as 50 to 60 pounds.
It’s common, though, for people’s weight loss to plateau at six to eight months, after which they are at risk of regaining that weight, said Dr. Maria Collazo-clavell, an endocrinologist at the Mayo Clinic. Research suggests that most people return to their previous weight within about four years.
For those who are successful at keeping off the weight, it’s not clear if the reason is genetics, health history or life circumstances, such as having a supportive partner, a stable job or time to cook, said Kevin Hall, a nutrition and metabolism scientist at the National Institutes of Health.
Why doesn’t the weight stay off?
When you lose weight, your body increases your appetite and reduces the number of calories you burn, Hall said.
He and others have estimated that for every two pounds of weight you lose, your metabolism slows by about 25 calories per day, and your appetite increases by about 95 calories per day. In other words, if you lose 20 pounds, your body will burn roughly 250 calories less each day while craving about 950 calories more.
To maintain weight loss through dieting over time, you’ll have to keep eating less while resisting a rising appetite and slower metabolism, which is “increasingly difficult,” Schur said.
The drive to eat more is so strong because our brains “sense that our energy stores are being depleted,” she added, and “that’s a threat to our survival.”
New weight loss drugs prevent weight regain in part by reducing normal appetite signals, Collazoclavell said. But when people stop taking the drugs, the weight returns, probably for the same reasons described above.
Are there health risks associated with dieting for weight loss?
Dieting often results in cycles of weight loss and regain, and some research has suggested this can be harmful, said Kendrin Sonneville, an associate professor of nutritional sciences at the University of Michigan School of Public Health.
Some studies have found that weight fluctuation is associated with earlier death, cardiovascular disease, Type 2 diabetes and depression; however, these studies sometimes include people who have lost and regained weight because of health problems, not just from dieting.
“There’s not conclusive evidence that it’s harmful to go up and down,” Schur said, but there is debate about the possibility.
Sonneville worries that dieting may put some people at risk of developing an eating disorder. Anecdotally, many people with eating disorders say their conditions began with dieting, she said. While clinical trials have not borne this out, those studies had many limitations and have not fully assessed how dieting affects “people’s relationship with food and their bodies in the long term,”
Sonneville said, so more research is needed.
Most people who diet don’t develop an eating disorder, Sonneville said, but even then, their relationships with food can deteriorate if they start “prioritizing weight and nutrition over joy and culture and connection.”
If you have a difficult relationship with food and your body, or if you have experienced binge eating or another eating disorder, Schur said, it is more important to focus on a healthy relationship with food than on your weight.
If dieting doesn’t work, what should we do?
People think that if they just “grit their teeth and white-knuckle it through” a diet to lose 10 or 20 pounds, “they can start to relax,” Hall said. “That’s the wrong way to think about it.”
If you want to change how you eat in order to lose weight, you have to sustain those changes “for the rest of your life,” he added. “Otherwise, you’re going to regain the weight.” Given that, consider making changes you can stick with.
If you consume a lot of ultraprocessed foods, reducing your intake can be sustainable. Short-term research has shown that those who consume mostly ultraprocessed foods tend to eat more and gain more weight than those who eat minimally processed foods, though Hall acknowledged that lack of time, money and access to whole foods are all potential barriers to making this change.
Collazo-clavell advised adopting a Mediterranean eating pattern, which focuses on healthy fats, whole grains, legumes, nuts, fruits and vegetables. Having at least two or three square meals each day can help you feel full and be less likely to overeat at night, she added. And avoid eating within three hours of going to bed, which is associated with weight gain.
Getting regular physical activity can also help keep the weight off and has other benefits, including a longer life and a lower risk of dementia, Schur said.
Ayana Habtemariam, a dietitian in Arlington, Virginia, encourages clients — many of whom have spent decades dieting — to practice intuitive eating. This involves tuning in to your body’s hunger and fullness cues more deeply, and redefining success so that you can feel happy regardless of your size, she said.
All of the experts we spoke with agreed on one point: People will benefit from adopting healthy habits, “even if they don’t lose a pound,” Collazoclavell said.