Why We Gain Weight As We Get Older

Fat cells in 54 subjects were studied over an average period of 13 years; during that period the subjects showed decreased lipid turnover in fat tissues, regardless of whether they gained or lost weight. Lipid turnover is the rate by which lipid/fat in the cells is removed and stored, those that failed to compensate for the decrease by intaking fewer calories gained weight by an average 20%.

Additionally, lipid turnover was also examined in 41 women who underwent bariatric surgery, and how the lipid turnover rate affected their ability to keep weight off 4-7 years after their surgeries. Those who had a low rate before surgery managed to increase their lipid turnover and maintain weight loss; these subjects were believed to have had more room to increase their lipid turnover than those who already had a high level pre-surgery. 

"The results indicate for the first time that processes in our fat tissue regulate changes in body weight during ageing in a way that is independent of other factors," says Peter Arner, professor at the Department of Medicine in Huddinge at Karolinska Institutet and one of the study's main authors. "This could open up new ways to treat obesity."

Exercising more has been shown to speed up lipid turnover in fat tissue, this research supports this and further indicates that long term results of weight loss surgery would improve if combined with increased physical activity. 

"Obesity and obesity-related diseases have become a global problem," says Kirsty Spalding, senior researcher at the Department of Cell and Molecular Biology at Karolinska Institutet and another of the study's main authors. "Understanding lipid dynamics and what regulates the size of the fat mass in humans has never been more relevant."