Taking Control of Your Dietary Composition Part 2

If you’ve read the previous series and effectively taken control of your energy balance, it means that you’re now ingesting an amount of energy each day that is consistent with your objectives for affecting body composition. For example, if you’re looking to maintain your current weight, you’ll be taking in the same amount of energy that you expend such that equilibrium will be maintained. On the other hand, if your goal is to gain or lose, you will have set up an increment or deficit that was appropriate for that purpose. For example, to lose a pound of fat over the course of a week, you would take in 500 calories less than you expend each day to get that job done. And that would hold true no matter which food sources you chose to supply your energy. So, the take-home message is that taking control of your energy balance is straightforward at least in theory. However, energetic balance is only half the battle. Once you know how many calories you should be consuming, the next step is to figure out the best way to get them.

The energy we derive from the foods and liquids we ingest is stored in chemical bonds. When we eat the food or drink the liquid, we break down the bonds to release the energy. Carbohydrate, fat and protein are energy sources within these foods that are each structured differently and each of these macronutrients also serves specific roles within the body. Consequently, ingesting the appropriate amount of energy without regard for the source does not provide for optimal health. This is why it is essential to take control of your dietary composition once you have done so with your energy balance.

Deciding how to best allot your calories with respect to macronutrient consumption can be challenging because many different theories abound. For example, low-fat diets that were popular in the ‘80s and ‘90s were eventually supplanted by restricted carbohydrate ones like the Atkins and South Beach that were based on the notion that such an approach was more effective for promoting fat loss. The flaw in this reasoning was that fat loss depends solely on the energy content of the diet, so if energy intake is controlled for, macronutrient proportion should make little difference in this regard. Generally speaking, the energy contained in the macronutrients is relatively consistent across different foods despite some variance with regard to digestibility. Consequently, a decision regarding how much of each to take in should be based solely upon how much of each your body needs. Average values of net energy content for each macronutrient are conveniently rounded to whole numbers known as Atwater General Factors. These factors are four, four and nine calories per gram for protein, carbohydrate and fat, respectively.

In conjunction with the Atwater General Factors, reference daily intake values for the three macronutrients that have been established by the United States Department of Agriculture can be used to balance macronutrient consumption. These recommendations are expressed relative to the total amount of calories you consume. For example, the USDA recommends that 10-35 percent of total energy intake comes from protein. This means that if you are taking in 2,000 calories per day, 200-700 of those calories should come in this form. Given that each gram of protein contributes four calories to the diet, the recommended protein intake in this case would be 50-175 grams. The recommended ranges for carbohydrate and fat is 45-65 and 20-35 percent, respectively, so performing the same calculations reveals that a 2,000 calorie-per-day diet should comprise 225-325 grams of carbohydrate and 44-78 grams of fat. Importantly, the USDA also specifies the types of fat you should predominantly consume as they suggest that saturated fat should be limited to less than 10 percent of total calorie intake (22 grams for the preceding example) while trans fat is restricted to as little as possible.

The USDA percentages and Atwater General Factors provide a good way to roughly estimate the amount of each macronutrient you should consume per day in conjunction with the appropriate energy intake. However, the ranges are somewhat broad. A good way to narrow it down is to consider precisely how much of a macronutrient you require based upon your body weight. For example, the long-standing recommendation is to eat 0.8 grams of protein per kilogram body weight each day to satisfy your body’s needs. However, more recent research suggests that this minimal level might be sufficient only for sedentary individuals that have relatively low requirements. Conversely, in those who are active and exercise regularly, as much as 1.8 grams per kilogram might be appropriate. Interestingly, this is especially true for endurance athletes, who can require even more protein than those involved in more vigorous activities like resistance training. This is because in addition to using protein to satisfy structural requirements (e.g., to provide the building blocks for tissue repair), these athletes also use a significant amount to energize their exercise sessions. Endurance athletes also often consume as much as 6-9 grams of carbohydrate per kilogram body weight for the same purpose.

This article was originally published in New Living Magazine, which can be accessed on-line at www.newliving.com.





Go back