How long does it take for training results to show up? According to a recent study, you can expect beneficial changes after only one workout. The study was presented at the American Physiological Society’s Integrative Biology of Exercise V conference in Hilton Head, South Carolina. The subjects were five obese women. In one phase the women overate but did no exercise. In the next phase they again overate but then exercised. The researchers found that the body’s fat oxidation capacity was reduced after one day of overeating. One day of exercise, however, increased the rate of fat oxidation.
A major cause of insulin resistance is excess intramuscular fat, or fat stored within muscle—usually more of a problem with sedentary people. In those who work out regularly, intramuscular fat becomes a readily available energy source. Conversely, the excess intramuscular fat in those who are inactive produces noxious substances that encourage insulin resistance, substances that never build up in active exercisers because the fat is burned up.
When the women in the study overate, they took in 700 calories above normal, or baseline, intake, and when they exercised, they expended the same 700 calories. What’s interesting about the study is that the beneficial effects happened with just the one workout.
One lesson to be learned from this study is that if you overeat, you can neutralize the fat-promoting effects of those extra calories through activity. The other lesson is that such changes occur quite rapidly.