Jonathon Stavres, PhD, ACSM-EP-C
It is well accepted that there are two main components to weight management, exercise, and diet. It may take a team of exercise physiologists and registered dietitians to completely understand how these two components interact. We will review some very basic concepts related to exercise and diet that will help explain why you may not be losing the weight you think you should be.
A registered dietitian can assess an individual, and prescribe a very specific diet that will best meet that person's needs. The reality is that a large number of people don't see or have immediate access to a registered dietitian. For those people, weight management boils down to one fundamental concept; calories consumed verse calories expended. Often times, and especially in the cases of those who have just begun regular exercise, people tend to think that enough exercise can account for a poor or unchanged diet. We will compare the caloric cost of common activities and compare that to the caloric content of common foods.
Caloric cost of activity vs. Caloric content of food
Equations for specific activities (walking, running, cycling, etc.) can be found in the American College of Sports Medicine's Guidelines for Exercise Testing and Prescription 9th edition (2014). Let’s begin with walking.
Let's say that you walk for thirty minutes per day, three days per week. Assuming a walking pace of three miles-per-hour (mph); a 130 lb female will burn 306 Kcals per week (a Kcal is the metabolic equivalent to a food calorie), and a 220 lb male will burn 518 Kcals per week. That would be approximately the same as one McDonald's Cheeseburger per week for the female (300 Kcals), or one McDonald's Big Mac burger for the male (549 Kcals). One pound of fat is equal to 3500 Kcals. Therefore, 1.5 hours of walking at three mph per week account for roughly one burger, or between 8% and 16% of a pound of fat.
Now let's say that you decide to exercise a little harder, and a little longer. Now you are running at six mph (a relatively good pace for a non-athlete) for thirty minutes a day for five days a week. A 130 lb female will burn 1577 Kcals per week and a 220 lb male will burn 2669 Kcals per week.
This would be approximately 5 McDonald's Cheeseburgers a week for a female, and just under 5 Big Mac's per week for a male. These results are a little more promising (45-76% of a pound of fat), however, these results come from what would be a relatively demanding exercise program. You may be asking, what does this mean?
The key to weight management is caloric balance
Imagine exercising all of that time, but then gaining all of those calories back due to a poor diet. The key to weight management is balance, specifically a negative or neutral calorie balance. Every person has an average daily energy expenditure, which can be increased with physical activity; and an average daily energy consumption, which can be increased with excess or improper food ingestion. In order to lose weight, calorie expenditure has to outweigh calorie consumption. This is why we must not exercise to eat but instead exercise and eat to live well.
*Before starting an exercise or nutrition regimen, consult with a physician and/or healthcare provider and a registered dietitian
**For more examples of other variations/exercises look under Multimedia-VDF Exercise Tips
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Article’s Resources
Pescatello, L. S., Arena, R., Riebe, D., & Thompson, P. D. (2014).ACSM'S guidelines for exercise testing and prescription. Baltimore, Maryland: Lippincot & Wilkins