Weight loss is easily the number one most common goal in any new personal training client that I see, even if they don’t say so. Many people would like to lose a few pounds of fat whether they want to acknowledge it or not. Our motivations for weight loss can be different. Some people may come to this decision for health reasons, while others are motivated by aesthetics or some other reason personal to them. The specific motivation and what type of motivation that is (intrinsic vs extrinsic) is very important for achieving any goal but I’m not going to get into that for this discussion.
For this post I just want to talk about the physiology of how to lose weight. I’ll start with some background info so we have an understanding of some of the basics of metabolism. Your body needs energy to survive and work properly. The energy your body uses comes from the food you eat. The measurement for this energy is the dietary calorie (calorie), one calorie is the amount of energy needed to raise the temperature of one kilogram of water one degree Celsius.
The foods we eat have varying amounts of calories depending on their composition. Food comes in three basic forms called macronutrients: 1. Protein 2. Carbohydrate 3. Fat
Protein and carbohydrate contain 4 calories per gram, while fat contains 9 calories per gram.
Metabolism in a basic sense refers to how many calories your body uses to function. The tissues in your body use energy to function, how this happens is a long discussion that we don’t need to get into right now. Tissues such as muscle use calories while fat does not, fat is actually an energy reserve. The muscles of your body use lots of calories while they are working, therefore a body that has more muscle mass will have a higher metabolism. Your basal metabolic rate (BMR) represents the amount of calories your body will use to simply survive in a day. Your activity level will add to this amount. You can calculate your BMR with this equation:
For men: BMR = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) + 5
For women: BMR = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) – 161
(if math is not your thing you can find calculators online that will do the work for you – just search BMR calculator!)
You can now use the Harris Benedict formula to calculate your daily caloric needs based on your activity level.
• If you are sedentary (little or no exercise) : Calorie-Calculation = BMR x 1.2
• If you are lightly active (light exercise/sports 1-3 days/week) : Calorie-Calculation = BMR x 1.375
• If you are moderately active (moderate exercise/sports 3-5 days/week) : Calorie-Calculation = BMR x 1.55
• If you are very active (hard exercise/sports 6-7 days a week) : Calorie-Calculation = BMR x 1.725
If you are extra active (very hard exercise/sports & physical job or 2x training) : Calorie-Calculation = BMR x 1.9
(note: these calculations are estimates to be used as a guide)
When you know these basic principles, weight control becomes easy to at least understand. You eat food to acquire calories for the cells of the tissues in your body to use. Your body will use a certain amount of calories in a day that can vary depending on how much activity you do. If you consume more calories in a day than your body uses, it will store those calories as fat. If you consume less calories in a day than you use, your body will access its calorie reserves in the form of fat and sometimes protein. In the most basic way this is how you gain or lose weight. Consume more than you use and you gain weight, consume less than you use and you lose weight, it’s that simple.
So why is it so hard to lose weight? The reasons are abundant and different for everyone but I believe that education is the foundation to overcome weight control issues. Counting calories is not a weight loss strategy that generally works very well on its own, however knowing how your body works in at least a basic sense is the first step to healthy and sustainable weight loss.
Next post, strategies for weight control.