Exercise programs designed to help obese men and women to reach a healthier weight tend to result in limited weight loss. Researchers at the University of New South Wales write in the Journal of Obesity that fat people should actually train for shorter amounts of time than coaches usually get them to do – but far more intensively. Interval training is ideal for people who want to lose weight.
Coaches and personal trainers helping people to lose weight through exercise often get them to cycle or jog a moderate intensity for 30-40 minutes three times a week. Sustained exertion at a level where you can still just hold a conversation – this is optimal for fat burning, the story goes.
In theory this approach should work, in practice the results are nothing to write home about. This is probably because fat people still consume more calories than they can burn with 2-3 hours of moderately intensive exercise.
Part of the solution, according to the Australians, is to change the exercise programmes. Short-duration high-intensity explosive exertion may burn fewer calories than longer duration moderately intensive exercise, but the body uses relatively high amounts of energy to recover from explosive exertion.
So you may well expend more energy over a period of several days as a result of a 15-minute intensive training session than from a moderately intensive session lasting almost an hour. Here are more articles on the subject.
The Australians tested this approach in an experiment with 46 obese men. All were in their twenties, with an average BMI of 28-29 – dangerously close to 30. If you have a BMI of 30, and aren’t a power lifter or bodybuilder, you’re probably obese. Your overweight is so serious that it’s a danger to your health.
Half of the subjects went to the gym three times a week and cycled for 20 minutes. They did a 5-minute warming up, and then did short sprints of 8 seconds alternating with recovery periods of 12 seconds. The men trained at 80-90 percent of their maximal heart rate. They finished off with a 5-minute cool-down.
After 12 weeks these subjects had lost about 2 kg fat and their lean body mass had increased slightly.
“As this high intensity intermittent exercise program required minimal time commitment, it has implications regarding subject compliance with exercise interventions”, conclude the researchers. “Thus, physical activity prescriptions, which require the least effort, while still producing adequate reductions in subcutaneous and visceral fat are likely to be optimal and high intensity intermittent exercise would seem to fall under this category as subject’s total exercise commitment was 60 min per week.”
The effect of high-intensity intermittent exercise on body composition of overweight young males.
Heydari M, Freund J, Boutcher SH.
School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, NSW 2052, Australia.
To determine the effect of a 12-week high intensity intermittent exercise (HIIE) intervention on total body, abdominal, trunk, visceral fat mass, and fat free mass of young overweight males. Participants were randomly assigned to either exercise or control group. The intervention group received HIIE three times per week, 20?min per session, for 12 weeks. Aerobic power improved significantly (P < 0.001) by 15% for the exercising group. Exercisers compared to controls experienced significant weight loss of 1.5?kg (P < 0.005) and a significant reduction in total fat mass of 2?kg (P < 0.001). Abdominal and trunk adiposity was also significantly reduced in the exercising group by 0.1?kg (P < 0.05) and 1.5?kg (P < 0.001). Also the exercise group had a significant (P < 0.01) 17% reduction in visceral fat after 12 weeks of HIIE, whereas waist circumference was significantly decreased by week six (P < 0.001). Fat free mass was significantly increased (P < 0.05) in the exercising group by 0.4?kg for the leg and 0.7?kg for the trunk. No significant change (P > 0.05) occurred in levels of insulin, HOMA-IR, and blood lipids. Twelve weeks of HIIE resulted in significant reductions in total, abdominal, trunk, and visceral fat and significant increases in fat free mass and aerobic power.
PMID: 22720138 [PubMed] PMCID: PMC3375095