After a 16% weight loss, premenopausal women with overweight experienced metabolic adaptation associated with a longer time than predicted to achieve weight-loss goals, according to study results published in Obesity.

“Regardless of the extent of metabolic adaptation, its clinical relevance remains to be fully determined,” Catia Martins, MSc, PhD, professor in the department of clinical and molecular medicine and faculty of medicine and health sciences in the obesity research group at the Norwegian University of Science and Technology and the Centre for Obesity and Innovation Clinic of Surgery at St. Olav University Hospital in Trondheim, Norway, and the department of nutrition sciences at the University of Alabama at Birmingham, and colleagues wrote. “It was initially suggested that metabolic adaptation could be a potential explanatory mechanism for long-term weight regain (relapse) as well as resistance to weight loss.”

Researchers evaluated 65 premenopausal women with overweight (mean age, 36.4 years) with an average BMI of 28.6 kg/m² who followed an 800 kcal per day diet until their BMI reached 25 kg/m² or less. Body weight and composition were measured before and after weight loss, and dietary adherence was calculated through total energy expenditure determined by doubly labeled water and composition changes.

Metabolic adaptation was defined as a significantly lower measured vs. predicted resting metabolic rate.

Participants experienced a mean 16.1% (12.5 kg) reduction in body weight over 155.1 days. Dietary adherence, on average, was 63.6%.

After weight loss, measured resting metabolic rate (mean, 1,305 kcal per day) was lower than that predicted (1,351 kcal per day; P = .002).

This metabolic adaptation was a predictor of the length of time needed to reach weight-loss goal (P = .041) and remained after adjusting for confounders (P < .001).

There were no significant associations between metabolic adaptation and target weight loss, energy deficit or dietary adherence. There was also no significant association between metabolic adaptation and the rate of weight loss or the difference between observed and predicted rate of weight loss.

“It needs to be emphasized that this metabolic adaptation was seen after 4 weeks of weight stabilization following the active weight-loss phase and, as such, is probably much lower that what would be expected during the active weight-loss phase. … It is reasonable to expect that metabolic adaptation during active weight loss in the present study may have been closer to 110 kcal per day (46 × 2.42) than 46 kcal per day,” the researchers wrote.

“Further research should confirm these findings in a population of men and women with obesity,” the researchers wrote.

PERSPECTIVE

Fatima Cody Stanford, MD, MPH, MPA, MBA, FAAP, FACP, FAHA, FAMWA, FTOS

The concept of metabolic adaptation has become of interest as we recognize the heterogeneity of response to various modalities of interventions to achieve weight loss. In this study by Martins and colleagues published in Obesity, the research team sought to determine whether metabolic adaption played a role in the length of time necessary to achieve weight loss in a diverse cohort of premenopausal women with overweight. The authors concluded that metabolic adaptation ensues after 16% total body weight loss, and it increases the length of time to achieve weight-loss goals.

This study reaffirms that fact that with weight loss, it becomes more challenging to achieve weight-loss goals. This helps inform patients about the difficulty to achieve and maintain weight loss, and it demonstrates that these issues intensify as more weight loss occurs. When patients indicate that weight loss becomes more challenging over time, they should be informed that this metabolic adaptation is leading to their difficulty. This will help to validate their struggles while informing them that these issues align with their biology. Additional tools such as pharmacotherapy (anti-obesity medications), devices and/or metabolic and bariatric surgery might be necessary to assist patients to achieve their weight-loss goals and overcome metabolic adaptation.

Fatima Cody Stanford, MD, MPH, MPA, MBA, FAAP, FACP, FAHA, FAMWA, FTOS

Endocrine Today Editorial Board Member

Obesity Medicine Physician Scientist

Massachusetts General Hospital

Associate Professor of Medicine and Pediatrics

Harvard Medical School