Weight Loss Exercise: Aim for 300 minutes a week

But Kyle Flack, an assistant professor of nutrition at the University of Kentucky, began to wonder a few years ago if this result was inevitable. Perhaps, he speculated, there was a cap on people's post-exercise calorie compensation, which means that if they extended their exercise hours, they would lose fewer calories and lose weight.

For a study published in 2018, he and his colleagues explored this idea, asking obese, sedentary men and women to exercise enough that they burned either 1,500 or 3,000 calories a week while exercising. After three months, the researchers checked everyone's weight loss, if necessary, and used metabolic calculations to determine how many calories the volunteers had consumed in return for their exertion.

It found that the total averaged 1,000 calories a week of compensatory eating regardless of how much people had exercised. According to this calculation, the men and women who burned 1,500 calories a week with exercise had reclaimed all but about 500 calories a week, while those who burned 3,000 calories a week had a net weekly deficit of about 2,000 calories. (Nobody's general metabolic rate has changed much.)

Unsurprisingly, the group exercises the most weight lost. the others don't.

However, this study left many questions unanswered, said Dr. Flack. Participants had performed similar supervised workouts and ran moderately for 30 or 60 minutes five times a week. Would different lengths or frequencies of training sessions be important for people's calorie compensation? And what made people eat? Have the different amounts of exercise affected people's appetite hormones differently?

To find out, he and his colleagues decided to repeat much of the previous experiment, but this time with novel exercise plans. For the new study, published in Medicine & Science in Sports & Exercise in November, they gathered another group of 44 sedentary, overweight men and women, checked their body composition, and asked half of them to exercise twice a week start for at least 90 minutes until you've burned approximately 750 calories per session or 1,500 for the week. They could exercise any way they wanted – many chose to walk, some to other activities – and they wore a heart rate monitor to track their efforts.