"Some people  who are they  have no problem fitting regular aerobic exercise into their lives. The rest of us want to know how much we have to exercise to see health benefits. Now we have some answers You may want to go just a tad longer and harder than youd thought. Current government guidelines advise http adults to get the equivalent of at least   hours of moderateintensity aerobic exercise or  minutes of higherintensity exercise every week plus some strength training. In effect those guidelines say theres no particular benefit from working out harder other than saving time. To find out if thats true researchers at Queens University in Ontario studied different combinations of exercise intensity and duration in a group of  sedentary adults with abdominal obesity. Thats generally defined http as a waist circumference of more than  inches for women who arent pregnant and more than  inches for men. People with abdominal obesity are at higher risk of heart disease and early death than people with slimmer waistlines. All the exercisers were told to work out under supervision five times per week for  weeks. One group worked out at low intensity about  percent of maximum oxygen uptake VO max a measure of cardiovascular fitness for about  minutes per session  enough to burn  calories for women and  for men. That exercise prescription was about the same as in the government guidelines. The intensity was about equivalent to walking slowly said study author Robert Ross http a kinesiologist at Queens University. Another group exercised at the same low intensity but almost twice as long  about  minutes on average or five hours a week until the women had burned  calories and the men . Article continues after this message from our sponsor And a third group exercised at a higher but still moderate intensity  percent of VO max until theyd burned the same number of calories as the second group. That took about  minutes a day or . hours a week. That intensity was equivalent to brisk walking for the previously sedentary participants Ross told Shots. Note that were not talking about the allout sprints of highintensity interval training http A fourth group was told to do no exercise. All the participants were told to keep a food diary and to eat a healthful diet but to keep their calorie intake constant. They also wore accelerometers to track their physical activity during the rest of the day to make sure the more intense exercisers werent compensating with more time on the sofa. At the end of the study members of all three exercise groups lost an average of about  inches from their waist circumference. There werent differences between the three groups. The average exerciser also lost  to  percent of body weight. The takehome message here is that if youre consuming a healthful diet and engaging with exercise consistent with the guidelines youre going to see a benefit in your waistline and on the bathroom scale said Ross. The results httpannals.orgarticle.aspxarticleid were published Monday in Annals of Internal Medicine. But there was also a benefit from going just a bit faster Only participants in the higherintensity group saw an improvement in glucose tolerance a risk factor for heart disease. Its unclear whether the  percent improvement seen will be enough to cut their risk of heart disease though. The result makes sense since theres some previous evidence suggesting that higherintensity exercise is tied to improving how the body processes sugar said Neal Pire an exercise physiologist who puts together medically based training programs at HNH Fitness http in Oradell N.J. a program of Holy Name Medical Center. Strength training http can also improve glucose tolerance which is why its part of the government guidelines he told Shots. Cardiovascular fitness also improved in all three groups but the lowerintensity exercisers who went longer did better than those who went shorter and the higherintensity group did better still. Bottom line All the exercisers improved but the folks who did the best walked briskly for about  minutes five times a week. Ross suggests you walk as if youre late for a bus. It doesnt take a lot said Ross. Thats why our participants were so surprised. They didnt have to climb Mount Everest."