Women who are fit and healthy tend to burn more fat when they exercise than men, according to new research from a team of sports nutritionists. The research, consisting of two new studies by academics led by the University of Bath's Center for Nutrition, Exercise &Metabolism, analyzed the factors that most influenced individuals' ability to burn body fat in endurance sports.
How the body burns fat is important to all of us for good metabolic health, insulin sensitivity and to reduce the risk of developing type II diabetes. But for endurance competitions, such as running or cycling, the way the body burns fat can make the difference between success and failure.
Previous research by the same team has shown how, for endurance athletes who compete in distance events, the carbohydrate stores in the body are quickly depleted during exercise. This means that athletes' ability to tap into their fat reserves to fuel them becomes essential to their performance.
The first study involved 73 healthy adults aged 19-63 (41 men; 32 women). It tested lifestyle and biological factors for optimal fat burning by asking participants to participate in a cycling fitness test and by measuring core indicators. Their results showed that women and those who were physically fitter, across the entire age range, burned fat more efficiently during exercise.
The second related article went a step further to investigate which molecular factors in our muscles and adipose tissue determine how fat is burned. In this experiment, the researchers took fat and muscle biopsies from the participants to analyze how differences in the proteins in fat and muscle tissue could affect their ability to burn fat.
It found that the proteins in muscle involved in breaking down stored fat into the smaller fatty acids, and proteins involved in transporting those fatty acids to the mitochondria in the muscles (the powerhouse of the cells) consistently correlated with a larger ability to burn fat. However, the molecular factors examined did not explain why women burned more fat than men.
Lead author of both papers, Ollie Chrzanowski-Smith of the University of Bath, explains:“Our study found that women tend to have a greater reliance on fat as a fuel source during exercise than men. Understanding the mechanisms behind these sex differences in fuel use may help explain why being a woman appears to provide a metabolic benefit for insulin sensitivity, an important marker of metabolic health.”
The researchers note that the ability to burn fat for fuel appears to protect against future weight gain, making for good weight management. However, they caution that the body's ability to burn fat should not be equated with its ability to lose weight. Losing weight is mainly caused by an energy deficit (ie consuming fewer calories than we consume). For weight loss, especially in overweight individuals, they emphasize the importance of diet and exercise.
dr. Javier Gonzalez, also from the Department of Health at the University of Bath, added:“Weight management is mainly about energy balance, so to lose weight we need to eat fewer calories than we expend through our resting metabolism and physical activity. A higher ability to burn fat as fuel appears to be somewhat protected against future weight gain, which may be related to the influence of fat burning on food intake and energy expenditure.
“Ultimately, a greater capacity to burn fat for fuel has potential benefits for endurance athletes by slowing the time point when they run out of precious carbohydrate stores.”
