LET SCIENCE GUIDE YOUR WAY TO...
by Dr Megan Chircop
Have you ever wondered why some people say that “weight loss is 80% diet”?
There are a number of ways that you can estimate or measure the energy-cost of physical activity. Some people use pedometers that have a built in algorithm that estimates total daily energy expenditure. Other people use the built-in calculators on their treadmill or exercise bike.
The bad news is that most of these methods tend to overestimate the effect of physical activity on total daily energy expenditure.
Not only that, but they often quote the “total calories burned” for the period of time that the equipment was used. It is possible that some people misinterpret this figure as being the amount of extra calories burned by the physical activity, which is actually significantly less than the number quoted.
Estimates of total daily energy expenditure with equations and calculators in widespread use rely on an estimation of basal metabolic rate (a calculation which usually takes into account your height, weight, age, gender etc.). This number is then multiplied by another number, which effectively adds more energy expenditure based on general activity levels. Compared to complete bed rest and no physical activity, sedentary individuals apparently clock up an extra 20% more calories per day just sitting and looking at screens. However, a marginal increase in physical activity (e.g. intense physical activity for about 20 mins, up to 3 times a week) will increase your total daily energy expenditure by another 17.5%. Similarly, increasing your physical activity further (to a total of 3-4 weekly sessions of 45 minutes of exercise) will get you another 17.5% more calories expended over the course of the day.
Now, I would suggest that it is unusual that people would go from being sedentary to training intensely for 45 minutes, 3-4 times a week. Keep in mind that a typical resistance training workout contains about a total of 8 minutes of intense physical activity, and that most people tend to perform either low-intensity steady state cardio or else high intensity interval training (which might only contain 6 minutes of moderately intense to highly intense physical activity).
The reality is that people are unlikely to train at a high intensity for their whole workout session.
Instead, long-term effective changes in physical activity are bound to be more subtle. One might gradually work up to the ideal of 45 minutes of moderately intense physical activity 3 to 4 times per week.
In the meantime what is happening to your total daily energy expenditure? And how about your total daily calorie intake?
Well, some studies have demonstrated that two things tend to happen when you consciously increase your physical activity levels:
When you factor in those last two points, successfully changing your conscious activity levels is unlikely to contribute significantly toward your total daily energy expenditure. Conversely, reducing your daily calorie intake by 20% is relatively straightforward, and this is usually generates enough of a calorie deficit to result in noticeable weight-loss. Hence the prevailing wisdom “you can’t out-train a bad diet”, and “weight-loss is 80% diet”.
Does this mean that exercise is a waste of time? NO!
For a number of reasons.
So, the take home message is simple.
To lose weight and keep it off, you need to increase your physical activity levels permanently and you must eat the right amount of calories to nourish your body without starving yourself or over-eating.
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Welcome. I am Dr Megan Chircop. I am a medical scientist and nutritionist with 20 years in medical research. As such, I have extensive knowledge and a thorough understanding of how the body works. I am able to simplify the science behind the way food fuels the body and mind to provide energy and nutrition needed to achieve optimal health and vitality. I am also a keen sportswoman, and have extensive knowledge of sports nutrition.
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