Sweat it out: Exercise more crucial than dieting in preserving weight loss, study finds

02 Apr 2019 --- Physical activity is more important in maintaining achieved weight loss than dieting, according to a new study from the University of Colorado Anschutz Health and Wellness Center (AHWC). Published in the March issue of Obesity, the study found that people who exercise maintained their weight despite consuming the same amount of calories per day with those who did not exercise.

“This study addresses the question of why so many people struggle to keep weight off over a long period,” says Danielle Ostendorf, Ph.D., a Postdoctoral Fellow at the AHWC.

“By providing evidence that a group of successful weight-loss maintainers engages in high levels of physical activity to prevent weight regain – rather than chronically restricting their energy intake – is a step forward to clarifying the relationship between exercise and weight-loss maintenance,” she says.

The debate on whether diet or exercise is more effective for weight loss seems to always gravitate towards highlighting the importance of nutrition. Research has shown that maintaining a caloric deficit in order to lose weight is more important, while exercise may boost the results and promote better health. 

“The truth is that both [nutrition and exercise] are important, not just in terms of weight loss (you could achieve it with either alone) but in terms of long term health and well-being. Fuel and move your body,” Aisling Pigott, Dietician at the British Dietetic Association (BDA), tells NutritionInsight in response to the report.

Doubly labeled water method
The researchers followed people who successfully lost weight and compared them to two other control groups. One group was comprised of subjects with a normal BMI (Body Mass Index) and similar to the BMI of those who lost weight and one group whose participants were overweight or obese. The participants who maintained their weight loss had a weight of about 150 pounds(68kg), similar to the normal weight controls, while overweight controls had a body weight of roughly 213 pounds (104kg).

This study is one of the few to measure total daily energy expenditure in weight-reduced individuals using the gold standard doubly labeled water method. Doubly labeled water is water in which both the hydrogen and the oxygen atoms have been replaced with an uncommon isotope of these elements for tracing purposes. The method allows researchers to accurately measure an individual’s energy expenditure by collecting urine samples over one to two weeks after people are given a dose of doubly labeled water.

Using doubly labeled water provides a more accurate estimation of energy intake and better insights on energy expenditure. Previous studies have used questionnaires or logging nutritional information to measure energy intake and these methods have significant limitations.

During the study, the researchers also measured every participant’s resting metabolic rate, to determine what portion of the total daily expenditure is from energy expended at rest versus energy expended during physical activity. Prior studies used self-reported measures or activity monitors to measure physical activity, which hasn’t prove as accurate a technique.

Important outcomes
According to the study’s findings, people who successfully lost weight are more reliant on physical activity in order to maintain their weight loss, rather than calorie restriction. In the study, successful weight loss maintainers were individuals who maintained a reduced body weight of 30 pounds(13kg) or more for over a year.

People who maintained their weight burned approximately 300 calories a day more than the normal weight control group, but not significantly more than the overweight/obese group.

Of the total calories burned, the amount burned in physical activity by weight loss maintainers was significantly higher (180 kcal/day) compared with that in both individuals of normal body weight and individuals with overweight/obesity. Despite the higher energy cost of moving a larger body mass incurred by individuals with overweight/obesity, weight loss maintainers were burning more energy in physical activity, suggesting they were moving more.

Weight loss maintainers also showed higher levels of steps per day (12,000 steps) when compared to the normal weight group (9,000 steps) and the overweight/obese group (6,500 steps). 

“Our findings suggest that this group of successful weight loss maintainers is consuming a similar number of calories per day as individuals with overweight and obesity but appear to avoid weight regain by compensating for this with high levels of physical activity,” explains Victoria A. Catenacci, MD, a Weight Management Physician and Researcher at AHWC. 

The findings are consistent with results from the longitudinal study of "The Biggest Loser" contestants, where physical activity energy expenditure was strongly correlated with weight loss and weight gain after six years.

“Exercise is an important part of health and lifestyle. However, exercise can look different for different people. For some, it might be running or gym, but for others, it can be as simple as walking up the stairs. It may be a better use of language to call it ‘movement’ or ‘activity,’” concludes Pigott. 

By Kristiana Lalou