Fat by the Numbers

Wouldn’t it be great if every part of improving or maintaining our health could be reduced to a numeric equation?


Given the inherent differences between individuals – lifestyles, interests and genetic predispositions to name a few – that seems extremely unlikely.

But while we may not be able to solve all of our physiological mysteries to within three decimal points of accuracy, we can still use a few basic calculations to keep our bodies headed in a healthy direction.

Fat by the Numbers

Fat loss is a commonly expressed goal for many new fitness training clients.  Part of a fitness trainer’s responsibility is to explain the basics – and the importance – of healthy weight maintenance. And for that, numbers can be most useful.

Let’s look at one commonly used equation: 3,500 calories equals=1 pound of body weight. Let’s say someone accustomed to a daily caloric intake begins consuming considerably more calories – say 1,000. Without other changes in this person’s daily lifestyle to use this additional 1,000 calories, every 35 days, this means the gain of a pound of body weight. Take this over the course of a year, and that weight gain amounts to over 10 pounds. With few exceptions, all ingested calories in excess of a weight maintenance intake results in weight gain. While such an example is unlikely in real-world practice (daily caloric intake can vary greatly, as can daily caloric use), it does illustrate how weight gain can happen over time. Weight gain from fat, then, can happen for two primary reasons:

An Increase in Caloric Intake over a Maintenance Level

Although there can be a number of factors that contribute to it, weight gain can be viewed as a matter of mathematics. As mentioned, the human body under normal conditions requires an increase of 3,500 calories over a maintenance intake to result in a body weight increase of 1 pound , assuming all other diet, exercise, and metabolic factors are unchanged. This means that raising the calorie count by 500 calories/day will result in a weight gain rate of 1 pound/week (7×500=3,500). If the caloric intake increase were only 250 calories/day the rate of weight gain would be only 1 pound every 2 weeks (14×250=3,500). In addition, increasing caloric intake by 1,000 calories/day over a maintenance intake will result in a weight gain rate of a whopping 2 pounds/week. With all that in mind, even a slight increase in total caloric intake, given sufficient time and consistency, has the potential to result in a long-term overweight condition. In such cases, one option is to change dietary habits.

However, drastic attempts at dieting can result in a starvation response that leads to slowed metabolism and even greater fat gain. Because of this, it is recommended that one reduce dietary intake by 500 calories per day to achieve an optimum weight loss rate of one pound per week. Fats and carbohydrates are the advisable categories of nutrients to cut down on. Reducing protein intake from a maintenance diet can result in lean tissue loss.

A Decrease in Activity

That same caloric arithmetic applies to activity, albeit in the reverse direction. A decrease in activity means a savings of energy. A savings in activity calories is the same as an increase in dietary calories. Another way of saying this is that a reduction in activity leads to an increase in weight. The converse is that activity can be increased in order to lose fat. For example, let’s say someone’s past maintenance intake has been 2,500 calories/day and that this person now wishes to lose fat. Instead of dieting to lose fat, the individual chooses to increase activity expenditure to lose fat. A typical 1-hour aerobic/low level activity exercise session (performed at 60-85% average intensity) yields an expenditure of approximately 500 calories. As a rule-of-thumb, with all other variables constant, every seven of these sessions will result in a weight loss of 1 pound (7×500=3,500). As people become less active, there is a greater likelihood of significant weight gain. If the activity reduction is unavoidable, this can be countered temporarily with an equal decrease in dietary caloric intake.

So, in the above example, for every session of activity reduced, that would mean removing 500 calories from the diet. That’s not always practical, however. When fat loss is the goal, and whenever there is an option, it is always healthier to increase activity than to crash diet.


1. The National Federation of Professional Trainers. Sports Nutrition Manual. 2nd Ed. Lafayette, IN: NFPT, 2006.


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.