An exercise topic that has the subject of debate for years is how many calories does one burn after an exercise session. What type, how long, and how intense does a session of exercise need to be? A recent paper in the journal Medicine & Science in Sports & Exercise trumps earlier studies because of its careful design, according to lead author Amy A. Knab, of Appalachian State University.

In this study, Dr. Knab, recruited 10 men, ages 22 to 33, who agreed to spend two periods of 24 hours each in a metabolic chamber, a small room that measures the calories people burn while they are inside. They were not all athletes, but they had to be able to ride a bike vigorously.

On the first visit to the chamber, the subjects had to sit perfectly still, sitting in a chair and moving only to eat meals. They were permitted to a two-minute stretch every hour during the afternoon. They burned, on average, 2,400 calories on this sedentary day.

The second visit to the chamber came two days later. Everything was identical, except that the subjects rode a stationary bike at a high intensity for 45 minutes.

The exeercise itself burned 420 calories, but what was most interesting was the calories burned afterward. Over the next 14 hours, the men burned an extra 190 calories, increasing the total calories burned by 37 percent!

The authors were surprised-they had expected some calories burned but not so many. They concluded that the intensity of the exerciase was what caused such a pronounced effect. The subjects cycled at an intensity of 70% of their VO2 max, a level at which conversation is difficult.

A different study, also using a metabolic chamber, tested the effects of moderate exercise and found no afterburn. Those subjects exercised at a rate of 50% VO2 max, which allows for conversation.

A recent book that Dr. Claude Bouchard and colleagues edited noted two studies that found this effect. The researchers found that if subjects ran at 70% VO2 max or cycled at 75% VO2 max, they could burn 300 to 700 extra calories after the exercie was over, although 700 was rare.

The effect may be due to post-exercise metabolism: the body starts using more fat and less carbs after a hard exercise session. Several hormones that are released during exercise remain elevated in the blood afterward, increasing metabolism. Also, extra calories may be used when the muscles replentish glycogen, the sugar stored in muscles.

This all seems to fit in with the high-intensity exercise (H.I.T.) I’ve been promoting for some time. Add to that the mini-fasts (no breakfasts) after exercise and the body will be burning almost all fat during that time. Why not give it a try a couple times per week? Please let me know the results.

Stay well, John R Blilie, M.S.