• Weight loss followed by weight regain may cause fat gain and muscle loss in individuals who are overweight and obese and at a high risk of diabetes.
• Muscle loss and fat regain may accelerate ageing, leading to muscle weakness and frailty, with consequences for metabolic and gut health. 
• Though meal replacement products and medications can help people lose weight quickly, most regain weight once they stop using them.
• More research is needed to investigate the implications of these therapies on long-term health.

In individuals with overweight and obesity and at a high risk of diabetes, weight loss followed by weight regain may increase body fat and reduce muscle mass, a new study reports. 

“Anything that acts to increase the loss of fat-free mass [muscle] can…be thought of as accelerating the ageing process with implication for the longer-term risk of muscle weakness and frailty,”  Tom Yates, professor of physical activity, sedentary behaviour and health at the University of Leicester and lead author of the study, said in a press release. 

“This study raises important questions around the longer-term implications of weight loss followed by weight regain has on body composition and long-term physical health,” Yates said.  

The study, “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”, was published in Diabetes, Obesity and Metabolism. 

Overweight and obesity significantly increase the risk of type 2 diabetes. And unfortunately, the global rates of obesity and type 2 diabetes are rapidly increasing. Scientists predict that by 2035, over 50% of the world’s population will be obese, and over 643 million will have type 2 diabetes by 2030. These conditions are costly to global economies, and the cost burden is anticipated to worsen. 

Studies have revealed that reducing body weight by 5-7% can reduce the risk of type 2 diabetes by up to 90% in individuals with overweight and obesity, as long as the weight loss is maintained for at least three years. As such, healthcare providers recommend dietary and lifestyle changes for weight loss and sometimes prescribe meal replacement products or medications, such as semaglutide (Ozempic), to hasten and support it.

However, losing weight and keeping it off can be challenging for most people, as they tend to regain weight after stopping strict diets or medications. If the weight regained consists primarily of fat, it can negatively affect overall health by accelerating ageing, increasing inflammation, and disrupting metabolic and gut health.

In this study, scientists in the United Kingdom investigated how weight loss and regain affect body fat and muscle mass in people with overweight and obesity and at risk of type 2 diabetes. 

How Weight Regain Affects Body Fat and Muscle Mass

The researchers enrolled 622 participants (average age 63 years, body mass index [BMI] of 32) from 10 primary care practices across Leicestershire, UK. Of these, 59.6% were classified as obese. Participants’ weight, body fat and muscle mass were assessed three times over two years.

During the first year of the study, 4.6% of the participants lost 5.23 kg of body fat and 1.88 kg of muscle. But in the second year, they regained all the body fat they had lost in the first year and also lost 0.98 kg of muscle mass. Over two years, they lost a total of 1.5kg of muscle. 

Another group of participants, comprising 5.4% of the total, gained weight in the first year, which they later lost in the second year. This group gained 1.9 kg of muscle mass in the first year but lost all of it in the second year. However, they still retained 1.71 kg of body fat.

The study found that 70% of the weight loss came from body fat in individuals who maintained weight loss over two years. However, for those who gained weight over the same period, 73% of the gained weight was body fat.

“What was particularly interesting to us was that the individuals who lost and regained weight went on to regain all of their fat mass but lost 1.5kg of fat-free mass. This equates to about a decade of ageing,” Yates said. “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”, Yates added. 

Previous research suggested that individuals who are older and those with a normal BMI are more prone to regaining body fat after losing weight compared to those who are overweight and obese. However, this study and recent studies contradict this claim. A study conducted in 2020 on women with obesity found that weight regain led to a gain of 4kg in body fat.

The researchers highlighted some limitations to their study, such as using predominantly White participants and bioelectrical impedance analysis (BIA) to measure body fat and muscle mass instead of the gold standard DEXA scan. 

“Given the increase in licenced weight loss therapies, which may be used for limited time periods and data from dietary interventions showing weight regain after initial weight loss, there is some urgency in investigating whether these results are replicated with different therapies used to achieve initial weight loss and, if replicated, the wider implications on longer-term ageing-related health risks, including frailty”, the researchers concluded.

The Main Message

People who are overweight or obese and at risk of diabetes are just as likely as older adults or those with normal BMIs to regain fat and lose muscle if they regain weight after losing it. 

Unfortunately, regaining weight after losing it can speed up ageing and adversely affect metabolic and gut health. With the growing use of weight loss products and medications that speed up weight loss, it is vital to research the possible consequences of weight regain since most people regain weight once they stop using these products. 

It may be beneficial to focus on behavioural therapies that encourage long-term changes in diet and lifestyle habits to minimise weight regain, particularly in populations at risk of diabetes.