This is the second of my three-part series on how to lose body fat. My previous article addressed the most effective exercise strategies for reducing body fat. As I mentioned before, fat loss occurs in response to a negative energy balance. This means that excess body fat is oxidized when energy intake is less than energy expenditure.
Anyone who intends to lose excess body fat must make a decision about how to achieve a negative energy balance. The choices are to eat less, exercise more, or both.
For many people, once the decision to reduce body fat is made, there is a sense of urgency. Armed with the goal of rapid fat loss, athletes may combine severe caloric restriction with frequent and intense bouts of exercise. Is this an effective strategy?
Eat Less and Exercise More?
This approach is likely to end in failure for most because a) physical activity depends on the availability of energy, and b) caloric restriction limits energy availability. When low calorie diets are combined with intense training, the inevitable outcomes include
- exhaustion
- overtraining
- catabolism (muscle loss)
- discouragement
- binge eating
- acceptance of mediocre physical development
Not surprisingly, most will abandon this strategy quickly and cite poor willpower or “genetics” for the lack of results. The reality is that drastic measures taken to reduce weight are unnecessary and likely to result in poor adherence to a fat loss program. Without program adherence, there is no hope for success. Thus, one must identify a strategy for losing body fat that is both effective AND sustainable. With a moderate increase in activity and a moderate decrease in energy intake, fat loss occurs at a slow but consistent rate. For some, a moderate pace is acceptable and comfortable; for others, it’s unbearably slow.
If you’re attempting to achieve rapid fat loss, identify the strategies that have the greatest impact. Dieters often focus on macronutrients (e.g., high protein, low fat, or low carbohydrate diets), but achieving a negative energy balance should always be the primary goal. The next question, of course, is whether to emphasize exercise or diet to create an energy deficit large enough to have a substantial impact on fat loss.
The Advantage of Caloric Restriction
If maximizing the rate of fat loss is your goal, dietary strategies are generally superior. This is because, for anyone who’s not a serious endurance athlete, the energy deficit that can be achieved through caloric restriction (eating less) is considerably greater than that which can be achieved through activity. For casual athletes, physique-only athletes, or off-season athletes, reduced calorie diets are preferred for fat loss. When used correctly, caloric restriction can help the athlete to avoid the problems of fatigue, muscle loss, and appetite enhancement that often accompany high levels of endurance training.
It’s important to consider “how much is too much?” when reducing calories. Energy intake below the basal metabolic rate (BMR, or the amount of energy required to support the body’s functioning at complete rest), is not typically recommended by dietitians.
One reason for this guideline is that eating below BMR puts the athlete at risk for muscle loss, particularly if the reduced calorie diet is combined with intense exercise. A second reason is that, for the in-season athlete, attempting to lose weight through caloric restriction can have a negative impact on performance if energy demands for the activity are not met. A third reason is that very low calorie diets (VLCD) may compromise health if they contain insufficient levels of essential nutrients. Finally, low calorie diets may cause cravings that lead to binge eating. For these reasons, energy intake below BMR should be avoided.
Using BMR and Calorie Cycling
There are several formulas used to estimate BMR. An online calculator can be used to simplify the process. Estimates vary as a function of weight, sex, age, and body fat percentage. The accuracy of the estimate increases when body fat percentage is known. For the sedentary individual with an office job, BMR x 1.2 provides an estimate of the energy expenditure for the day. As activity increases, the energy requirements increase. Enter your relevant data into this calculator for an estimate.
When participating in normal daily activities (no exercise), eating at BMR will result in the loss of body fat. On workout or competition days, when performance is more important than fat loss, reduced calorie dieting is not recommended. On these days, eat to support the activity. This calorie “cycling” will allow fat loss to occur without impacting athletic performance.
If you’re overwhelmed by the prospect of calculating BMR and using activity multipliers, there is a simple but less accurate way of determining basal and maintenance energy intakes. For weight loss, multiply weight in pounds by 10 on non-workout days; for workout or competition days, multiply weight by 12 or more (depending on the intensity and duration of the activity). This approach will require more trial and error, but some prefer this strategy because of its simplicity. Adjust the multiplier if there are negative fat loss or performance outcomes. For example, if weight loss occurs too quickly, multiply weight in pounds by 11 instead of 10. Similar adjustments can be made for workout or competition days.
Examples in Practice
Energy intake estimates for casual athletes with weight loss goals:
1) A 200 lb. man who lifts weights for 30-45 minutes, 2-3 times a week. On non-workout days, he would consume approximately 200 x 10 = 2000 calories; on workout days, 200 x 12 = 2400 calories. If he loses weight but also loses muscle mass and strength, he should increase his activity multiplier of 12 to 13 on workout days.
2) A 140 lb. woman who plays in a local tennis league for 2 hours each Wednesday and Saturday. On non-workout days, she would consume approximately 140 x 10 = 1400 calories; on competition days, 140 x 13 = 1820. If she loses weight but lacks energy during tennis matches, she could increase the activity multiplier to 14 or 15 on competition days.
Expect to lose 1 to 2 pounds of body fat each week with this approach. By decreasing energy intake on rest days and eating at maintenance on workout or competition days, you will also be able to maintain muscle mass and performance. When body fat loss goals are ultimately achieved, increase calorie consumption on rest days to maintenance levels.
To summarize the diet section of this series, for fat loss,
- achieve a negative energy balance by eating less instead of exercising more
- BMR can be used to establish calorie intake on non-workout days for maximum fat loss with minimal side effects
- calorie cycling should be used by athletes to achieve fat loss without sacrificing performance
In the next and final installment of my three-part series on how to lose body fat, I’ll cover program adherence and explain how the strategies presented in this three-part series can be integrated to support athletic performance AND an ideal body composition. Check out part three here.
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I'm Joel Minden, PhD, licensed clinical psychologist, cognitive behavior therapist, sport psychology consultant, and strength and conditioning specialist.