Fit and healthy females tend to burn more fat when they exercise than men, according to new research. And people who are able to burn fat as fuel are protected against future weight gain, reports a team of British sport nutritionists. The two studies by the Centre for Nutrition, Exercise & Metabolism at the University of Bath analysed factors that influence individuals’ capacity to burn body fat when undertaking endurance sports. The way the body burns fat is important for good metabolic health, insulin sensitivity and reducing the risk of developing type 2 diabetes. For endurance sport competitions, such as running or cycling, the way the body burns fat can make the difference between success and failure. “Our study found that females typically have a greater reliance upon fat as a fuel source during exercise than males. Understanding the mechanisms behind these differences in fuel use may help explain why being female seems to have a metabolic advantage for insulin sensitivity,” said lead researcher Ollie Chrzanowski-Smith. The first study , published in the International Journal of Sport Nutrition & Exercise Medicine , involved 73 healthy adults aged 19 to 63. It tested the lifestyle and biological factors for optimal fat burning by asking participants to take part in a cycling fitness test and measuring key indicators. Participants took part in an incremental cycling test which increased in intensity over time. The cyclists rode until exhaustion point, which was between 20 to 30 minutes. The results found that females and those who were physically fitter, right across the age ranges, burnt fat more efficiently when exercising. “The ability of females to tend to be more reliant upon fat as a fuel source during exercise compared to males is likely due to differences in oestrogen concentrations and its subsequent physiological effects,” explained Chrzanowski-Smith. “Additionally, various ‘machinery’ within the body that is involved in burning fat may be upregulated [increased] in females compared to males. For example, studies have found sex differences in fat transporters and how fat is stored within skeletal muscle.” The second related study , published in the journal Experimental Physiology , took this a stage further to explore what molecular factors in muscles and fat tissue determine how fat is burnt. How this father shed 27kg (60lbs), helped by his family and community This experiment involved researchers taking fat and muscle biopsies from participants to analyse how differences in the proteins in fat and muscle tissue might affect their ability to burn fat. It found that the proteins in muscle that are involved in breaking down stored fat into the smaller fatty acids, and proteins involved in transporting those fatty acids into the mitochondria in muscle (the powerhouse of the cells) consistently correlated with a greater ability to burn fat. The research also found that the ability to burn fat as a fuel appears to protect against future weight gain, ensuring good weight management. Researcher Dr Javier Gonzalez 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. “However, people with a higher ability to burn fat as a fuel seem to be somewhat protected against future weight gain, which might be related to how fat burning affects food intake and energy expenditure.” “ Previous research from the same team has shown how, for endurance athletes competing in distance events, the body’s carbohydrate stores deplete quickly when exercising. This means that an athlete’s ability to tap into their fat reserves to fuel them on becomes essential to their performance. “Ultimately, a greater capacity to burn fat as a fuel has potential benefits for endurance athletes, by delaying the time point when they run out of precious carbohydrate stores.” Meanwhile scientists from the Department of Physiology of the University of Granada have shown that drinking a strong cup of coffee before exercise can increase the rate of fat-burning. Caffeine consumption in supplements is commonplace for athletes despite scarce scientific evidence about its beneficial claims. The study, published in the Journal of the International Society of Sports Nutrition, concluded ingesting 3 mg/kg of caffeine 30 minutes before aerobic exercise did significantly increase the rate of fat-burning. They also found that if exercise is performed in the afternoon, the effects of the caffeine are more marked than in the morning. The researchers also debunked the myth that exercising on an empty stomach was the best way to lose weight. “The recommendation to exercise on an empty stomach in the morning to increase fat oxidation is commonplace,” said lead researcher Francisco José Amaro-Gahete. “However, this recommendation may be lacking a scientific basis, as it is unknown whether this increase is due to exercising in the morning or due to going without food for a longer period of time.” The findings suggested that a combination of a strong dose of caffeine followed by moderately hard aerobic exercise in the afternoon created the optimal conditions for increasing fat burning.