Using Exercise to Lose Weight: Intensity or Time?

More and more people are turning to exercise to lose weight. That’s a good thing, since exercise strengthens the heart, muscles, bones and even the brain, which low-calories diets do not do. However, a question often comes up: to lose fat, should we do moderate exercise for a longer period of time or vigorous exercise for a short period of time?

First you should know that we are talking about aerobic exercise here, in other words, exercise that works the major muscle groups (especially the thighs and hips) for a certain period of time. This type of effort increases metabolism, which, in turn, increases calorie expenditure. These are the best exercises you could do to lose weight. They can be done at moderate or high intensity. Intensity is considered moderate if you are a bit hot and are breathing quicker than at rest. Intensity is high if you are hot and breathing quickly without actually becoming out of breath. Some examples include cross-country skiing on flat ground, snowshoeing in shallow snow, speed-walking or light winter jogging, swimming (aquafitness or swimming pool lengths), or using a cardiovascular exercise machine (stationery bike, elliptical machine, treadmill, step machine, etc.).

Put the Main Focus on Duration

This is a realistic approach. If you want to lose weight, and you are not in shape, you will find it easier to do moderate exercise versus high-intensity exercise. Thus, you will be less likely to injure yourself or hurt your health. An unfit person who starts straight into vigorous exercise has a far higher risk of doing so. So, by putting the emphasis on duration, you give yourself the chance to exercise every day and control your weight. If you exercised intensely, you would have to sometimes take days to rest to allow your muscles to recuperate.

This being said, how long should you practise moderate aerobic exercise? The best thing to do during the first few weeks is to schedule in three ten-minute sessions of exercise (or two 15-minute sessions) during the day, if possible every day. The idea is to stimulate your metabolism two or three times a day, for a total of 30 minutes of moderate physical activity, which is the minimum amount of exercise recommended by experts for people to remain healthy. This plan will help you use up about 150 calories more per day, or 1,000 more per week. And, after three-and-a-half weeks, you will have burnt 3,500 calories more than usual. That’s equal to 400 g or almost a pound of fat! If you want to speed up weight loss and are very motivated, you can gradually increase your total exercise sessions to 45 minutes a day. You will lose, more or less, one pound of fat in less than 2.5 weeks as long as you do not increase the calories you eat.

Secondly: Intensity

After one month of moderate aerobics, you will have improved your physical condition and started to lose weight. You can then think about increasing your training. There are two advantages to higher intensity exercises: better cardio and more calorie expenditure per minute. This is important to know if you have a very busy schedule. For example, if you weigh 70 kg and jog at a steady pace for 20 minutes, you burn off about 160 calories. To expend the same number of calories while speed walking, you would need at least 30 minutes. By doing more vigorous exercises, you also create a larger “energy debt” for your body. In other words, after doing so, your metabolism remains high and you continue to burn calories for two or three extra hours without lifting a finger! This post-exercise burn, often “forgotten” when calculating the number of calories used, is immense, especially if you exercise several times a week.

Compromising with Intervals

The major problem with intense exercise is that you could lose motivation in the long run. Therefore, it is worthwhile to integrate more intense work into moderate exercise sessions: in other words, interval training. Let’s say you speed walk at about 110-120 steps per minute. During your 10-to-15- minute session, walk even quicker for about 30 seconds every two minutes at a pace of about 130-135 steps per minute. You can apply the same principle to swimming, cross-country skiing, winter jogging or running on a treadmill. Why are intervals beneficial? They increase the number of calories burnt without increasing the time you exercise. In concrete terms, you will still be exercising for 30 minutes a day, but you will be burning 1,300 calories a week instead of 1,000.

In fact, interval training provides great results for those who want to lose weight and improve their health through exercise. A study at the Centre of Preventive Medicine and Physical Fitness at the Montreal Heart Institute confirmed the effectiveness of this type of exercise. Nine months after following the Kilo-Actif program (in French,, 62 obese people participating in the study lost an average of 5.5% of their body mass and 5.15% around their waist. Moreover, they had increased their physical ability by 15%. Their bad cholesterol (LDL) had dropped by 7%, and their good cholesterol (HDL) had climbed by 8%. And all that in under a year!

Move Every Day: A Must for Weight Maintenance

Recently researchers at the Mayo Clinic in the USA revealed the essential role that daily physical activity plays in regulating our weight. Twenty subjects (10 slim and 10 obese) were equipped with a sophisticated system for evaluating daily calorie expenditure and then monitored for ten days. They noticed that the slim subjects burned approximately 350 calories more per day than their obese counterparts. Also interesting: the obese subjects were sedentary for two hours longer per day.