Weight regained after weight loss results in less muscle, more fat, study finds

A Leicester study that measured the fat mass and fat-free (muscle) mass of dieters suggests that weight loss followed by weight regain has a negative impact on muscle mass.

The findings of the study, carried out by the National Institute for Health and Care Research (NIHR) Leicester Biomedical Research Centre (BRC) research team and published in the journal Diabetes, Obesity and Metabolism, looked at the body composition of 622 adults at-risk of type 2 diabetes.

The lead author, Tom Yates, Professor of Physical Activity, Sedentary Behaviour, and Health at the University of Leicester, said, "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 But sadly, weight regain is common over the longer term with all diets or once obesity therapies are withdrawn. 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" behavioral 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.

Professor Yates said, "Fat-free mass 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 behaviors. 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."

The study found although the majority of participants maintained their body weight with no change to fat mass or fat-free mass, some (4.5% of observations) lost over 5% of their body weight between the start of the study and 12 months, and then regained it over periods of between 12 to 24 months.

Professor Yates continued, "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. 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."