Even though exercise burns calories, it is important to maintain this calorie deficit by reducing dietary intake as well – the old “calories in and calories out” adage holds true.
In a study published in the British Journal of Sports Medicine in September, 58 obese people participated in a 12 week study of aerobic exercise without any dietary adjustments. The average weight loss was 7 pounds, and many lost only half this amount.
It is possible to target your exercise routine for weight loss - “If you work out at an easy intensity, you will burn a higher percentage of fat calories” than if you work out a higher intensity, says Dan Carey, Ph.D., an assistant professor of exercise physiology at the University of St. Thomas in Minnesota, who studies exercise and metabolism.
Carey has developed formulas to optimize the maximal fat oxidation during exercise. In his study, maximal fat oxidation (MFO) occurred at 54.2% maximal oxygen uptake (V̇O2max). However, the great variability between individuals suggests that a laboratory test is required for exact results. For the general population, their MFO lies between 60% and 80% of their maximal heart rate.
It has been well documented that regular endurance training increases the ability of the body to use fat as a fuel during exercise. Another recent study looked into the “afterburn effect” - in the past, it has been suggested that a bout of exercise elevates the heart rate for a prolonged period post-exercise, and has a calorie-burning effect. Researchers at the University of Colorado School of Medicine in Denver found that subjects did not use additional body fat on the day when they exercised. In fact, most of the subjects burned slightly less fat over the 24-hour study period when they exercised than when they did not.
Edward Melanson, Ph.D., an associate professor in the division of endocrinology at the School of Medicine and the lead author of the study says that “it all comes down to energy balance,” or, as you might have guessed, calories in and calories out. People “are only burning 200 or 300 calories” in a typical 30-minute exercise session, Melanson points out. “You replace that with one bottle of Gatorade.”
All is not lost however, as the studies reinforced the additional benefits of exercise, beyond weight reduction. In the study of obese people who took up exercise, most became notably healthier, increasing their aerobic capacity, decreasing their blood pressure and resting heart rates. This lead the authors to conclude that:
“significant and meaningful health benefits can be achieved even in the presence of lower than expected exercise-induced weight loss. From a public health perspective, exercise should be encouraged and the emphasis on weight loss reduced”.
Read more: Phys Ed: Why Doesn't Exercise Lead to Weight Loss?, NY Times and British Journal of Sports Medicine Study