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Identify Your Timing Needs

This is an excerpt from Nutrient Timing by Lauren Link.

Understanding your energy needs is important, but especially so for athletes. When calculating energy needs it’s important to understand the different categories that contribute to your total needs, or total daily energy expenditure (TDEE). These three categories are as follows:

  1. Basal metabolic rate (BMR). Your BMR is the number of calories that your body needs over the course of 24 hours just to support basic functions at rest, like breathing, digesting food, regulating temperature and pH, and maintaining brain function. Caloric needs are often much higher than what people anticipate, especially for very active individuals. Diets recommending as few as 1,600, 1,200, or even 800 calories per day are commonplace in the media and in certain fitness circles. However, these very low calorie suggestions may not even cover your BMR, let alone your daily activity. A common topic of interest in this area is the long-held belief that metabolism (which can be thought of as similar to BMR) declines steadily with age, beginning as early as age 30 or 40. However, a recent study by Pontzer and colleagues (2021) using a massive cross-sectional study cohort of over 6,400 individuals showed that BMR actually stays relatively stable until after age 60, at which point it begins to decline. The study also found that the decline in BMR was mostly attributed to loss in muscle mass rather than aging itself. With this in mind, it’s a good goal for adults (especially older adults) to maintain as much muscle mass as possible.
  2. Physical activity (PA). A large contributor to your total daily energy needs is your physical activity. This includes your workouts as well as activities of daily living like walking. For athletes this number can be quite high and—in some cases—almost equal to BMR. Similar to the effect of aging on BMR, physical activity can decrease over time because it tends to be harder to maintain the same intensity of exercise as you age. It’s therefore worth recognizing that the same amount of time spent exercising might not yield the same energy expenditure as you age or even just begin exercising less formally.
  3. Thermic effect of food (TEF). TEF refers to the energy expended to digest, absorb, and store the nutrients from the food you’ve just eaten. Although this number is not significant on its own, it does factor in slightly when understanding your TDEE.

Although calculating your energy needs can be helpful, it’s also important to recognize the limitations of such calculations. For one, estimations of your energy needs, caloric expenditure of certain activities, and even caloric content of certain foods are just that—estimations—and they depend on a number of different factors from day to day. It is also important to recognize your own limitations in handling this sort of information. If you have struggled with an eating disorder or disordered eating, or if you have the tendency to become very fixated on numbers, you are probably better off skipping this section and focusing on the more broad recommendations later in this chapter.

Calculating Basal Metabolic Rate

If you do feel like having an estimation of your daily energy needs would be helpful for you, proceed with the following calculations to determine your needs based on your physical activity. There are many equations that can be used to calculate energy needs, which use different anthropometric measures of varying nuance. The Mifflin-St. Jeor (1990) equation will be used here, largely because it is simple and considered one of the more accurate equations used to estimate BMR.

Males: (10 × weight in kg) + (6.25 × height in cm)
− (5 × age in years) + 5

Females: (10 × weight in kg) + (6.25 × height in cm)
− (5 × age in years) − 161

Factoring in Physical Activity

Once you’ve calculated your BMR, it’s important to calculate what your physical activity contributes to your total energy needs. To do so, first decide which of the following activity categories best describes you:

  • Sedentary. This reflects little or no exercise.
  • Lightly active (light exercise or sports 1-3 days per week). This might be reflective of off days or weeks or times that activity is very limited due to injury.
  • Moderately active (moderate exercise or sports 3-5 days per week). This might include lighter training periods when you are not training every day of the week and doing more strength and skill training with minimal conditioning.
  • Very active (hard exercise or sports 6-7 days per week). This would likely be reflective of normal training for many athletes, during which training is occurring most or all days of the week, for at least a couple of hours, with a mix of strength and skill training as well as conditioning.
  • Extra active (very hard exercise or sports and physical job or twice daily training). Examples of this would include athletes who are in a very high training load with heavy conditioning or very high mileage, or athletes who are practicing multiple times per day (including athletes who may be participating in multiple sports at once).

Now, multiply your activity level by your calculated BMR based on the following equations:

Sedentary = BMR × 1.2

Lightly active = BMR × 1.375

Moderately active = BMR × 1.55

Very active = BMR × 1.725

Extra active = BMR × 1.9

Calculating Thermic Effect of Food

To calculate an estimate of your thermic effect of food, multiply your BMR by 0.1. Add this to the number you just calculated for your physical activity.

With these three categories in mind, total daily energy expenditure (TDEE) for Jenny, Doug, and Thomas could be estimated as the following:

Jenny: 2,677 calories

Doug: 3,428 calories

Thomas: 4,116 calories

As mentioned, knowing their TDEE can be helpful for some, but for many people a less structured approach works just as well or even better. This is especially true for people who tend to get obsessive over calories eaten, calories burned, and their intake and activity in general. Obsession over these kinds of numbers can quickly lead to disordered eating tendencies, which are incredibly detrimental to health and performance. It also tends to be unrealistic to be extremely structured with these numbers, because life often doesn’t cooperate: It’s hard (and usually stressful) to try to plan for every single possibility when it comes to food and schedule. I often encourage athletes to approach their daily needs by focusing on eating every three to four hours, and by trying to balance their plate with carbohydrate, protein, and fruits and vegetables. Of course, which carbohydrates and proteins you choose are important, as is how your foods are prepared, but the simple habit of approaching your meals and snacks with this balanced outlook can go a long way toward promoting great habits without making you feeling stressed in the name of calories in and calories out.

More Excerpts From Nutrient Timing