Using BMR and ‘Daily Caloric Need’ to Gain or Lose Body Weight.

Let me start off by briefly going over some very basic, fundamental information about the constituents of the foods that we eat and how our bodies are able to utilize the calories, carbohydrates, proteins, and fats that make up these foods.

All of the foods that we eat, including meats, vegetables and fruits are made up entirely of either one or more of the following 6 fundamental nutrients:

1. Proteins
2. Carbohydrates
3. Fats
4. Ethanol (Alcohol)
5. Vitamins & Dietary Minerals
6. Fiber

Of these 6 components, the first four in the list all contain calories. Calories are basically the amount of energy stored within each of these nutrients. Calories are needed by the human body to fuel metabolism. Metabolism is the process responsible for turning food into the energy needed to support life. The two basic metabolic pathways responsible for the conversion of calories to energy are the anabolic pathways and the catabolic pathways.

Catabolism refers to the set of metabolic pathways in which molecules are broken down into smaller units causing a small amount of energy to be released in the form of heat, while the remaining energy is used to drive the synthesis of an energy transport molecule called adenosine triphosphate (ATP). ATP is basically a molecular form of stored energy and its formation allows the transfer of chemical energy from one metabolic process to another. The metabolic processes that use ATP as an energy source also convert it back into its precursors allowing it to be recycled continuously. The ATP, created during catabolism, is then available to fuel the processes within the other metabolic pathway – the anabolic pathway.

Anabolism is the set of metabolic pathways responsible for the construction of new molecules from smaller units. Anabolism is responsible for bone mineralization, cell differentiation and growth, and muscle growth.

Regulating calorie intake can affect both gaining body weight and losing body weight. Generally consuming more calories than the amount used by the body’s current metabolic needs will result in body weight gain. Conversely, consuming fewer calories than the amount needed by the body to fuel its current metabolic needs will result in weight loss. For someone interested in attempting to either gain or lose weight it is very useful to know how many calories are needed, on average, to fuel the body’s current metabolic needs. I will refer to this number as the ‘daily caloric need’. To determine the ‘daily caloric need’ it is necessary to first ascertain what is called the BMR or ‘basal metabolic rate’.

The human body burns calories 24 hours a day, even during sleep. The basal metabolic rate, which can be estimated by using the very simple formula you see below, is the number of calories the resting body would burn if absolutely no activity were performed in a 24 hour period.

Women: BMR = 655 + (4.35 x weight in pounds) + (4.7 x height in inches) – (4.7 x age in years).

Men: BMR = 66 + (6.23 x weight in pounds) + (12.7 x height in inches) – (6.8 x age in years).

Now that the BMR is known, applying an activity multiplier to this number will result in a fairly accurate estimate of the number of calories needed by the metabolism to fuel typical activity level and basic metabolic processes. Here I am using the Harris Benedict Formula.

To determine the ‘daily caloric need’, multiply the BMR by the appropriate activity factor, as follows:

1. If you are sedentary (little or no exercise) : Calorie-Calculation = BMR x 1.2
2. If you are lightly active (light exercise/sports 1-3 days/week) : Calorie-Calculation = BMR x 1.375
3. If you are moderately active (moderate exercise/sports 3-5 days/week) : Calorie-Calculation = BMR x 1.55
4. If you are very active (hard exercise/sports 6-7 days a week) : Calorie-Calculation = BMR x 1.725
5. If you are extra active (very hard exercise/sports & physical job or 2x training) : Calorie-Calculation = BMR x 1.9

Now that the ‘daily caloric need’ is known, it is very easy to figure out how many additional calories need to be consumed to gain weight or how many fewer calories need to be consumed to lose weight. For the person trying to gain weight, sufficiently increasing calorie consumption over the ‘daily caloric need’ will cause body weight gain. One pound of body weight is roughly equal to 3500 calories, so if the goal is to gain one pound of body weight a week, 3500 excess calories should be consumed during the course of one week. Therefore, if one takes 3500 and divides by 7 (days in a week), the resulting 500 calories is the number of extra calories that need to be consumed each day in order to reach this goal. The composition of the food calories consumed, i.e. the amounts of proteins, carbohydrates and fats, is also very important to promote lean muscular gain. See the article, Eating: Lean, Muscular, Weight Gain. While eating excess calories will invariably produce weight gain, it is important to remember that the goal is to gain ‘muscular’ weight, not to increase storage of body fat. When utilizing this method to gain weight it is highly recommended that considerably more intense exercise be performed to promote an increase in muscular weight gain.

For someone trying to lose weight, the same basic principles apply. 3500 calories is roughly equal to one pound of body tissue so therefore, limiting calorie consumption to 3500 below the ‘daily caloric need’ in one week should produce weight loss close to one pound a week. That’s 3500 divided by 7, giving a result of 500. So, 500 fewer calories than baseline (calculated above), need to be consumed each day to reach the goal for the week. Here again, the composition of the food calories eaten during this time is very important. See the article, Eating: Lose Weight & Retain Muscle. Unfortunately reducing calories can also negatively affect the metabolic rate, slowing it down, and therefore limiting the amount of weight that can be lost. To compensate for the slowing metabolism, an additional 30 to 45 minutes of cardio-vascular exercise, added to the daily exercise routine, will help stimulate metabolism and increases the number of total calories burned. At a body-weight of 175 lbs., 30 minutes of cardio exercise will burn between 300-500 calories. This increases the total daily caloric deficit to 800-1000 calories and the weekly deficit to 5600-7000. At 7000, that’s going to be very close to 2 pounds of body-weight lost each week.

Now it’s important to remember that this is merely a guideline and many, many other factors can, and will produce great variation among the individual results realized through the use of this approach. Genetic factors, general health, a prior history of exercise experience and poor diet or nutrition can all contribute to a decrease in the effectiveness of this technique. It truly is not possible to emphasize enough the importance of consuming good high quality protein, adequate amounts of long chain complex carbohydrates and at least some omega-3 fatty acids, particularly while attempting to either lose or gain weight.

Using BMR and ‘Daily Caloric Need’ to Gain or Lose Body Weight.
San Antonio Personal Trainer