Maintaining weight loss: Physical activity more important than diet

July 17, 2019
Slim stomach of young woman, thin body with perfect waist, showing her jeans after successful diet or sport training on isolated
The key to maintaining weight loss is physical activity, a study shows. Photo: Getty Images.

It’s tough to lose weight and keep it off. Research shows that the vast majority of people who lose weight from dieting gain the majority of the weight back within four to five years, and some even gain more.

A study released in 2016 that followed contestants from NBC’s “The Biggest Loser” reality weight loss competition found that after substantial weight loss (an average of 130 lbs), the contestants’ levels of a leptin, a hormone that regulates hunger, had dropped and so had their resting metabolic rate, meaning contestants likely experienced an increase in hunger and they burned calories at a lower rate. These physiologic changes persisted long-term, six years after the end of the competition. Not surprisingly, these contestants regained all or most of the weight they lost.

Maintaining weight loss

With news like that it may seem that losing a weight and keeping it off is nearly impossible. So why bother trying? But not all people who lose weight gain it back. There are people who have successfully lost a significant amount of weight – and kept it off.

A photo of Dr. Victoria Catenacci
Dr. Victoria Catenacci

Researchers from the University of Colorado Anschutz Medical Campus and the Colorado School of Public Health, headed up by endocrinologist Dr. Victoria Catenacci, looked at a group of people who had successfully kept the weight off to find out what they were doing.

Catenacci recruited 90 adults who met certain criteria and divided them into three groups. Members of the successful weight loss maintainer group had lost at least 30 pounds and had maintained that weight loss for at least one year. Two control groups included adults who were overweight or obese whose current BMI was similar to the pre-weight loss BMI of the weight loss maintainer group and a second group of people who had never been obese and had a similar current BMI as the successful weight loss maintainer group.

“We were interested in the patterns of physical activity in these three groups, but also the energy expenditures of these people to understand how the successful weight loss maintainers were able to maintain their weight,” said Catenacci.

She went on to explain that one reason weight loss maintenance is difficult is that the number of calories that people burn every day is reduced after weight loss due to the reduction in body size. To achieve energy balance and avoid weight regain at a reduced body weight, people need to either eat less and or move more than they did prior to weight loss in order to compensate for this reduction in calories burned.

A slower metabolic rate

Both resting metabolic rate (the rate at which we burn calories at rest) and physical activity energy expenditure (the number of calories we burn with movement) go down primarily due to the reduction in body mass.

“Basically, you’ve taken off this 50-pound backpack you’re carrying and you burn less calories with every movement of every day,” she explained. “In addition, when you lose weight you do lose some muscle mass and some organ mass and your resting metabolic rate is determined by your muscle mass and organ mass”.

But, do people who have lost weight suffer an additional drop in metabolism long-term as The Biggest Loser study suggested?

According to the latest research published from Catenacci’s dataset, the answer is not clear. “In our study, there was no consistent evidence to suggest that people who have lost weight and maintained their weight loss successfully experience this additional reduction in their resting metabolisms long-term,”says lead author of the study, Danielle M. Ostendorf, PhD, a postdoctoral fellow in the school of medicine in the division of endocrinology. In this sample, the successful weight loss maintainers lost an average of 60 pounds and maintained at least a 30 pound weight loss for an average of 9 years.

“The resting energy expenditure in the weight loss maintainer group was where it should be based on their body composition, their age and their gender,” Ostendorf said.

Why the contradicting findings? Ostendorf said that both studies were designed differently, with The Biggest Loser study following participants over time.

“It’s difficult to compare the two studies because The Biggest Loser study had a much stronger study design. They had estimates of the participants’ resting energy expenditures before they even lost the weight. Whereas our study was a cross-sectional snapshot, with only one data point in time for them,” explained Ostendorf. “So, while we found that people who lost weight didn’t have a lower resting metabolic rate than people of similar body composition who had not lost weight, we were not able to compare their metabolic rate to what it was prior to weight loss. This is something we plan to do in a new, ongoing weight loss study”.

“I think that part of it was also the amount of weight lost and the way people lost the weight. For ‘The Biggest Loser’ contestants, weight loss was very rapid. We don’t know how our weight loss maintainers lost their weight but the likelihood of it being similar to The Biggest Loser contestants is pretty low.”

Good news

But there was another bit of good news for people wanting to lose weight and keep it off. Ostendorf’s research paper, Physical Activity Energy Expenditure and Total Daily Energy Expenditure in Successful Weight Loss Maintainers, published in Obesity’s March issue, found that the successful weight loss group was eating a similar amount of calories as the group of adults who were overweight or obese. Both of those groups were consuming more than the normal weight group.

So, how were the formerly overweight people able to maintain their weight loss without significantly cutting back on their calories long-term? The research points to the high level of energy expended through physical activity.

In other words, for weight loss maintenance, not necessarily weight loss, physical activity is the key. Numerous abstracts and several research papers were presented and published based on information gathered from this three-group dataset. Many of the findings from this research confirm the importance of high levels of physical activity.

“We know diet is important to help you lose weight. But it’s really difficult to reduce your calories for long term, every day,” Ostendorf says. “So, we are finding in Dr. Catenacci’s studies that when people are doing high levels of physical activity, it allows them to eat a little bit more and it gives them that leeway. There’s a light at the end of the tunnel.”

About the author

Joelle Klein is a Colorado-based freelance health and lifestyle writer. She regularly writes for UCHealth Today, Colorado Health & Wellness Magazine and Bottom Line Health. Her articles and blogs have appeared in 5280, Skiing, Fit Pregnancy, Pregnancy, the Denver Post, PBS Next Avenue, AARP, and the American Lung Association, among dozens of other health-related print and digital publications.
Joelle earned her bachelor’s degree in English at New York University and her master’s degree in journalism at the University of Colorado at Boulder. She is a member of the Association of Health Care Journalists (AHCJ) and American Society of Journalists and Authors (ASJA). Joelle lives in Denver with her husband and their two daughters. In her limited spare time, she enjoys cooking, reading, hiking, biking, camping, theater, travel, and spending quality time with her family.