Despite what unscrupulous diet ‘gurus’ would have you believe, weight loss is all about calories. You can employ all manner of highly hyped diet gimmicks, but you simply will not lose weight (aside from temporary water or fecal losses) if you do not establish a calorie deficit. To lose weight, you must burn more calories in a given period of time than what you ingest. No one, and I mean no one, has ever demonstrated that it’s possible to lose weight comprised primarily of fat, when ingesting more calories than you expend.  It’s physically impossible.

The safest method of increasing calorie expenditure is via physical exercise. Both low-intensity and high-intensity exercise regimens cause an increase in calorie expenditure. For example, a 165-lb person cycling at a 10 mph pace for 60 minutes will burn around 375 calories more than if they had spent that time sitting. Not surprisingly, higher intensity activities such as fast cycling or running cause a greater number of calories to be burned than slow running or cycling. If our 165-lb subject cranks up his cycling speed to a brisk 15 mph, then he will burn an extra 1050 calories during a 60-minute ride.1-2

The calorie-burning benefits of higher intensity exercise don’t stop when you finish your workout. After low-intensity exercise, your caloric expenditure promptly returns to baseline levels. However, after intense exercise, your body will continue to burn calories at an accelerated rate for periods ranging from several hours up to 48 hours.

It’s important to keep the extent of this post-exercise calorie burn in proper perspective, as it is often overblown. A recent survey of the evidence found that up to an extra 100-200 calories per day can be expended in the 24-48 hours following a high intensity cardio session.3   While that’s no doubt better than a poke in the eye with a sharp stick, it’s not the kind of calorie boost you can rely on solely for fast fat loss progress.

If your primary goal is fat loss, then there is a limit to the number of calories you will burn using brief High Intensity Interval Training (HIIT) workouts. You’ll be pushing to burn 200 calories during a short Tabata-style* HIIT session that lasts less than 15 minutes. Add another 100 calories burned over the next 24 hours from increased post-exercise metabolism, and you still have a calorie burn of only 300 calories or less.

As several researchers have emphasized, the main calorie-burning effects of exercise occur during the actual exercise session itself. The calorie burn during exercise is influenced by both intensity and duration.4-7  Exercising at a more moderate but still reasonably high level of intensity (primarily in the 70-85% maximum oxygen consumption range) might not cause the same degree of excess post-exercise oxygen consumption and will cause a lower amount of calories to be burned per minute than brief but super intense HIIT, but the longer duration will result in a higher overall calorie expenditure.

For example, a 165-lb person stationary cycling at a vigorous pace (200 watts) for 45 minutes will burn 590 calories during the exercise session alone — around twice the total calorie burn that can be expected from a brief HIIT session.

The Long and Short of Cardio Training

When it comes to maximally increasing your fitness, research has shown HIIT to be the king of cardio. In contrast, if your primary goal is fat loss, then you must understand that HIIT will not cause the same calorie expenditure as longer duration cardio performed between 70-85% maximum oxygen consumption range.  This must be taken into account when structuring your diet and exercise regimen to create a calorie deficit.

When implementing a cardio program for fat loss, you have a number of options:

1. Focus on steady state cardio performed at 70-85% maximum oxygen consumption.

1. Focus on HIIT. Individuals pressed for time or whose focus is maximal fitness can rely on HIIT for their cardio workout, keeping in mind that the reduced calorie burn (as compared to steady state cardio) may need to be countered by tightening up their diet slightly.

1. Use a combination of steady state and HIIT cardio. For example, you may choose to do steady state cardio in the morning or during lunch break, then a brief HIIT session after your weight-training workout in the evening. That way, you get the best of both worlds:  the fitness boosting effect of HIIT and the heightened calorie burn from steady state cardio.

1. Use HIIT and steady state cardio in the same workout. For the iron-willed, another option is to perform an HIIT session, then continue doing steady state cardio for another 45 minutes or so.

*The Tabata Protocol is explained in Part 1 of this article published in the February 26th issue of Total Health Breakthroughs.

References

1. Ainsworth BE, et al. Medicine and Science in Sports and Exercise, 1993; 25: 71-80.
2. Ainsworth BE, et al. Medicine and Science in Sports and Exercise, 2000; 32 (Suppl): S498-S516.
3. Hunter GR, et al. International Journal of Obesity, Jun, 1998; 22 (6): 489-493.
4. LaForgia J, et al. Journal of Sports Science, Dec, 2006; 24 (12): 1247-1264.
5. Laforgia J, et al. Journal of Applied Physiology, Feb, 1997; 82 (2): 661-666.
6. Bahr R, et al. Journal of Applied Physiology, Feb, 1987; 62 (2): 485-490.
7. Gore CJ, Withers RT. Journal of Applied Physiology, Jun, 1990; 68 (6): 2362-2368.

[Ed. Note: Anthony Colpo is an independent researcher, physical conditioning specialist and author. Learn more about Anthony's latest book, The Fat Loss Bible, by clicking here.]

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