The ‘Magic’ Number

What about the number 3,500 stands out in your mind? Do you often use this number in dealing with clients? If not, you could be in need of a refresher.

It has long been known that 3,500 calories equate to a pound of body weight in the metabolically average, apparently healthy individual — with several exceptions. In this particular aspect, fitness can be reduced to a mathematical equation.

In a perfect world, you would first prefer to have the diagnostic capability to determine RMR (Resting Metabolic Rate). The term RMR is somewhat similar to the term BMR. This diagnostic test basically determines how many calories an individual expends at rest. Each individual has a unique RMR.

Generally speaking, those who have difficulty in losing weight will have a low RMR and those finding it difficult to gain weight will have a high RMR. The diagnostic determination of RMR is by far more accurate than the vague determination of BMR most of us will likely be using in determining resting caloric consumption.

Prolonged, extremely low calorie dieting will slow the metabolism even more and would be reflected in a follow-up RMR. For this reason, especially among those with already low RMRs, it is important to keep caloric consumption at or above RMR needs otherwise these already low RMR dieters will experience an even greater fat accumulation. Conversely, it is just as important to maintain RMR minimum intake among those with already high RMRs in order to prevent an undesirable starvation loss of body tissue.

People with low RMRs typically expend fewer calories during both daily activity and the performance of exercise than do those with high RMRs who are performing the same work. When considering total daily activity expenditures, this is something to keep in mind. With this issue addressed, we can get on with the application of the magic number: 3,500.

Diet and 3,500

The least attractive method of fat loss is unfortunately the most commonly used: Dieting!

First of all, when one diets, there is always the opportunity for the body to cannibalize muscles and not draw from its fat reserves. This is cannot be avoided, and only offset in degrees through performance of resistance exercise. Even during moderate dieting the body views fat reserves as being more valuable than lean muscle, especially if those muscles are not being used.

So, where do you draw the line when dieting?

This is where magic number 3,500 comes in. It is generally accepted that the optimum fat loss rate is achieved by consuming 500 calories/day below an individual’s weight maintenance intake = RMR+daily activity+exercise expenditure. At this 500 calories/day decrease, one should lose body weight at a rate of 1 pound per week (7×500=3,500). A diet any lower may result in unacceptable lean tissue loss.

Conversely, those wishing to gain weight should also use the magic number 3,500 to regulate their weight gain. When gaining weight, using resistance training in the process to optimize the lean weight increase and minimize the fat increase, the participant needs to keep additional calories at approximately 500/day over his or her weight maintenance intake = RMR+daily activity+exercise expenditure. Generally, these additional 3,500 calories (500 calories/day increase) will result in weight gain at a rate of 1 pound per week. Both fat loss as well as weight gain diets that are too extreme end up being counterproductive, resulting in either too much muscle loss, or too much fat increase, respectively.

Exercise and 3,500

The healthiest — although the most difficult — way to lose fat is to exercise. If one could perform activity with a caloric expenditure of 500/day, he or she will lose weight at a rate of 1 pound per week. With this in mind, where weight maintenance is concerned, an increased expenditure of 500 calories/day through exercise amounts to the same as reducing calories at a rate of 500/day. Conversely, a reduction of activity expenditure in the amount of 500 calories/day amounts to the same as a 500 calorie/day increase in calories. Once again, this is the ideal weight loss rate. Keep in mind when exercising, though, that intense aerobic activity causes lean tissue loss, and also that resistance exercise needs to be performed to minimize the lean weight loss while dieting.

For the weight gain fitness program participant, it is not recommended that he or she perform a significant amount of aerobic activity. Rather, it is recommended to perform heavy resistance training to optimize lean weight increase. Unlike the fat loss participant, the best method of weight gain is to increase calories, taking care to perform resistance exercise at moderate to high intensity to ensure against undesirable fat accumulation.

Diet and Exercise

Combining proper caloric intake with the right exercise program is the preferred method of achieving any weight maintenance goal, fat loss or weight gain. It is important to understand that if the participant is exercising and dieting, each of these two variables must be considered. For example, if a fat loss fitness program participant is expending 300 calories/day during exercise, the daily caloric intake need only be reduced by 200 calories. If the weight gain participant is expending 300 calories/day during exercise, the diet needs to be increased by 800 calories, offsetting this expenditure to arrive at the desirable 500 calorie/day increase.

In most cases, it is up to the personal trainer to exercise his or her best judgment in establishing the initial diet and exercise recommendations based on your initial, in-depth consultation. Only after this consultation will you have a clear picture of the new fitness program participant’s past level of activity, dietary behavior, and metabolic predisposition (high, low, average RMR).


These resources are for the purpose of personal trainer growth and development through Continuing Education which advances the knowledge of fitness professionals. This article is written for NFPT Certified Personal Trainers to receive Continuing Education Credit (CEC). Please contact NFPT at 800.729.6378 or [email protected] with questions or for more information.
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