What Every Dieter Should Know about Metabolism: Metabolism Basics

Metabolism is the rate at which our bodies burn calories in order to maintain our bodies, and perform work. Our metabolic rate affects our Total Daily Energy Expenditure (TDEE). Weight loss is a based on a fairly simple formula. If the energy we consume exceeds the energy we expend, we gain weight; if the energy we consume is less than the energy we expend, we lose weight. Therefore as dieters, it is important for us to understand the factors that will increase our metabolic rates. That is what this series of articles is about-increasing our metabolic rate in support of weight loss.

We burn calories every second that we are alive. We burn calories when we are sweating at the gym, eating, or even sleeping. Our metabolic rate describes how quickly we burn those calories. The faster our metabolic rate, the easier it is to lose weight. A faster metabolic rate also means that we can eat more without gaining weight.

Factors that Influence TDEE

Resting Metabolic Rate (RMR): This is the body’s rate of energy expenditure just to maintain body functions without introducing any work or exercise.

Thermal Effect of Food (TEF): Chewing, swallowing, digesting, and absorbing nutrients all require energy. Different foods require different amounts of energy. Later on we will be looking at the thermogenic properties of various foods and how we can positively influence our metabolism in support of weight loss.

Daily Physical Activity: Different levels of physical activity, (running, lifting, sitting, talking, etc.) expend different amounts of energy. Increasing our daily physical activity will increase our caloric expenditure.

Body Composition: Body composition is influenced by age, genetics, medication, gender, and even medication. But, the most important factor is the ratio of fat to lean body mass. The more muscle and less fat we have, the higher our TDEE goes. And, that’s a good thing for weight loss dieters.

Aging and Weight Loss

At about the age of 30, our metabolic rate declines by about 1-2% every ten years. If we continue to consume the same number of calories as we did in our youth without increasing our exercise, the result is weight gain and we may grow a paunch and take on the profile of the middle age spread. If we don’t increase our exercise level, our body composition, the percentage of fat to lean, increases in favor of fat. And, fat takes less energy to maintain than lean muscle or bone. Muscle takes about 20 more calories per pound to maintain than fat does.

The Tipping Point

As we lose lean muscle mass in favor of fat, we have less muscle with which to perform work and create more muscle. If we don’t notice what’s happening, we get on the downhill side of the energy equation and it becomes very difficult to expend enough energy to maintain, much less, lose weight. The good news is that when we begin a conditioning program that includes strength training and start to work our way up the energy curve, at some point we reach the tipping point and it begins to work in our favor. With more muscle, we can perform more work which creates more muscle, and more muscle takes more energy to maintain and thus increases our TDEE even when we aren’t working out.

The Answer to Yesterday’s Quiz

Yesterday I described the birthday dinner I cooked for my wife and asked which foods were thermogenic (increasing the TDEE) and which foods were the most thermogenic. The dinner consisted of grilled bison sirloin steak, baked potatoes with non-fat sour cream, Brussels sprouts, green tea, and okra, onions, tomatoes, and Tabasco sauce.

Answer to question 1: All foods are thermogenic, that is, they take energy to chew, swallow, digest, and absorb.

Answer to question 2: The foods in this meal that are considered most thermogenic are: Brussels sprouts, green tea, and Tabasco sauce. Later in this series on metabolism and dieting, I will list the most highly thermogenic foods.

Next: Muscle and Weigh Loss

Here is my recap from yesterday.

Daily Dietary Recap-5/27/2007
Calories	Protein	Carbohydrates	Sodium	Fat	% Calories from Fat
1170.29	71.16 g	173.21 g	965.10 mg	14.08 g	10.83%