Provided you're not consuming too many calories, any amount of exercise may help. About five hours of weekly exercise may bring the biggest weight loss for obese adults who are also watching their intake of fat and calories.
So say researchers including John Jakicic, PhD. Jakicic leads the University of Pittsburgh's health and physical activity department.
Jakicic and colleagues studied nearly 200 obese women for two years. Their results were presented in Vancouver, Canada, at the North American Association for the Study of Obesity's annual scientific meeting.
The women in Jakicic's study were about 37 years old. Their average body mass index (BMI) was 32. A BMI of 30 or more is considered obese.
The women all agreed to exercise. They were randomly assigned by the researchers to one of four workout plans:
- Moderate amount of moderate-intensity exercise
- Moderate amount of vigorous exercise
- A lot of moderate-intensity exercise
- A lot of vigorous exercise
Moderate amounts of exercise were designed to burn 1,000 calories per week. The plans requiring lots of exercise were designed to burn 2,000 calories weekly.
Rules for Eating
The golden rule of weight loss is that calories burned must exceed calories consumed. The study tackled both ends of that equation.
Besides exercising, the women also limited their intake of calories and fat.
They were told to consume 1,200 to 1,500 calories per day. Fat was to account for 20% to 30% of those calories.
Remember, the study lasted for two years. It wasn't a short exercise blitz or crash diet. Most women completed the study (172 women, or 90%).
Who Lost Weight?
All of the women who finished the study lost a significant amount of weight.
Those who lost the most weight reported logging 270 to 300 minutes of exercise per week. That's 4.5 to 5 hours weekly.
Here are the average percentages of body weight lost by each group:
- Moderate amount of moderate-intensity exercise: 4.9%
- Moderate amount of vigorous exercise: 3.7%
- A lot of moderate-intensity exercise: 6.5%
- A lot of vigorous exercise: 7.2%
Higher Bar for the Obese
The CDC recommends that all adults get at least 30 minutes of moderate exercise five times a week. That adds up to 150 minutes per week.
That amount wasn't designed with weight loss in mind. "More intense or longer periods of physical activity may be needed to control body weight," states the CDC's web site.
Jakicic agrees. "Clearly, overweight individuals have different exercise needs than the general public when it comes to increasing their energy expenditure," he says in a news release.
"Energy expenditure" means calories burned.
"To maximize weight loss and minimize weight regain, it appears that overweight individuals should supplement dietary changes with approximately 300 minutes of exercise each week, which is twice the amount recommended for health in the general public," Jakicic continues.
If Jakicic's results are on track, what do they mean in the real world?
Should someone exercise 45 minutes a day, six days a week, for a total of 270 minutes per week? Or would five, one-hour workouts do? Can each day's minutes be split into several shorter sessions?
Jakicic and colleagues call for more work to sort out the details.
Consult a doctor before starting a weight loss or exercise plan.