Weight regained after weight loss results in less muscle and more fat

A study by the National Institute for Health and Care Research (NIHR) Leicester Biomedical Research Centre (BRC) research team that examined the body composition of 622 adults at-risk of type 2 diabetes and measured the fat mass (FM) and fat-free (muscle) mass of dieters suggests that weight loss followed by weight regain has a negative impact on muscle mass.

Figure 1: Adjusted change in fat mass and fat-free mass after 24 months. Data adjusted for age, sex, ethnicity, blood pressure medication, lipid-lowering medication, smoking status, treatment allocation, baseline fat mass and baseline fat-free mass. p < .05 compared with reference, *p < .01 compared with reference. Credit: Diabetes, Obesity and Metabolism (2023). DOI: 10.1111/dom.15400

"The clinical and economic costs of obesity have driven an expansion in dietary interventions and pharmacological weight loss therapies. But sadly, weight regain is common over the longer term with all diets or once obesity therapies are withdrawn,” explained the study’s lead author, Tom Yates, Professor of Physical Activity, Sedentary Behaviour, and Health at the University of Leicester. “This study raises important questions around the longer-term implications that cycles of weight loss followed weight regain has on body composition and long-term physical health."

This study took a close look at observations made on people at risk of type 2 diabetes taking part in the "Walking Away from type 2 diabetes" behavioural intervention, which aimed to increase physical activity through walking. Participants' annual weight change was assessed over two 24-month periods. Body composition was measured by bioelectrical impedance analysis (BIA), providing details on their fat mass and fat-free mass, which was validated against dual X-ray absorptiometry (DEXA) scans.

"Fat-free mass (FFM) is all of your body parts that do not contain fat, of which the largest component is muscle mass. A loss of fat-free mass occurs with aging but can be further affected by lifestyle behaviours,” Yates added. “Anything that acts to increase the loss of fat-free mass can therefore be thought of as accelerating the aging process with implication for the longer-term risk of muscle weakness and frailty."

In total, 622 participants were included (average age = 63.6 years, body mass index = 32.0 kg/m2, 35.4% women), contributing 1163 observations. Most observations (69.2%) were from those that maintained their body weight, with no change to FM or FFM. A minority (4.6% of observations) lost over 5% of body weight between baseline and 12 months, which was then regained between 12 and 24 months. These individuals regained FM to baseline levels, but lost 1.50 (0.66, 2.35) kg FFM, adjusted for confounders. In contrast, those that gained weight between baseline and 12 months but lost weight between 12 and 24 months (5.5% of observations) had a net gain in FM of 1.70 (0.27, 3.12) kg with no change to FFM.

"What was particularly interesting to us was that the individuals who lost and then regained weight went on to regain all of their fat mass but lost 1.5 kg of fat-free mass. This equates to about a decade of aging,” Yates concluded. “This suggests that 'weight cycling' may be associated with a progressively worsening body composition, which could have knock-on effects for longer-term physical health."

The findings were published in the paper, ‘Impact of weight loss and weight gain trajectories on body composition in a population at high risk of type 2 diabetes: A prospective cohort analysis’, published in the journal Diabetes, Obesity and Metabolism. To access this paper, please click here