Chapter 8 – Weight Management
Assessing Caloric Balance
Individuals can use information on their own caloric expenditure and compare that to caloric intake to determine if the calories taken in are in balance with these being expended (if weight maintenance is the goal). If a person intends to lose weight they would create a caloric balance with more calories out than in. Likewise, a person intending to gain weight would take in more calories than they expend.
Calculating Resting Metabolic Rate
Resting metabolic rate is the total number of calories burned when your body is completely at rest. RMR supports breathing, circulating blood, organ functions, and basic neurological functions.
The Harris Benedict ( H&B) Equation:
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- Men: 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) – (5.677 × age in years)
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- Women: 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) – (4.330 × age in years)
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As an example, for a 38-year old female, who is 5’6” (167.6 cm) and weighs 145 pounds (65.9 kg), her RMR would equal approximately 1,411 calories.
This is the energy needed daily to maintain normal physiological function.
Mifflin-St Jeor Equation:
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- Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
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- Women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
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Using that same example and this equation, the female’s RMR would equal approximately 1,356 calories.
Potential Errors
These formulas imply that all individuals of the same gender, age, height and weight have the same RMR, a fact that is certainly not accurate. Your lean body mass will significantly influence RMR and should always be considered.
Below is an example of a formula that takes lean body mass into consideration:
Katch-McArdle Equation:
RMR = 370 + (21.6 x Lean Body Mass in kg)
Factors Influencing RMR
Age, genetics and even biological adaptations are non-controllable factors that may influence RMR.
A few of the controllable factors influencing RMR are:
- Use of stimulants – thermogenic effects of stimulants such as caffeine can temporarily increase RMR
- Lean body mass – building lean body mass is an effective way to increase RMR, loss of lean body mass as a person ages is a factor in RMR lowering as a person gets older.
- Sleep – lack of sleep can negatively impact RMR
- Low caloric intake – the practice of eating very low caloric intakes (e.g., starvation, 800-calorie diets) can suppress RMR, a number that by some estimates can be as high as 20%.
Calculating Total Daily Energy Expenditure (TDEE)
In addition to RMR, a person would factor in calories burned through activity to find their Total Daily Energy Expenditure (TDEE).
To estimate physical activity level choose the activity multiplier that best represents your lifestyle:
- Sedentary: Little to no exercise. BMR x 1.2
- Lightly Active: Light exercise 1–3 days per week. BMR x 1.375
- Moderately Active: Moderate exercise 3–5 days per week. BMR x 1.55
- Very Active: Hard exercise 6–7 days per week. BMR x 1.725
- Extremely Active: Very intense exercise daily or a physically demanding job. BMR x 1.9
Next, multiply your BMR by the activity multiplier you chose to get your TDEE:
A 30-year-old man, weighing 70 kg (154 lbs) and 180 cm (5’11”) tall, who works a desk job and exercises 3-5 times per week.
BMR: (10 × 70) + (6.25 × 180) – (5 × 30) + 5 = 700 + 1125 – 150 + 5 = 1680 calories
Activity Level: Moderately active.
TDEE: 1680 (BMR) × 1.55 (activity multiplier) = 2604 calories
TDEE of approximately 2604 calories is the estimated number of calories this person needs to eat daily to maintain current weight. To lose weight, consume fewer calories; to gain weight, consume more.
Tracking Caloric Intake
As discussed in Chapter 7, a person can use nutrition apps/food logs to calculate Daily Caloric Intake (DCI) in addition to daily nutrient content of the diet.
Evaluating Caloric Balance
To evaluate your caloric balance, you can compare your daily caloric intake with your TDEE.
TDEE-DCI = Caloric Excess (positive number) or Caloric Deficit (negative number)
TDEE of approximately 2604 calories is the estimated number of calories the example person above needs to eat daily to maintain current weight.
If this person had a Daily Caloric Intake (DCI) of 2100 calories they would lose about 1 lb per week.
If this person had a DCI of 2800 calories they could gain 1lb about every 18 days or almost 2lbs per month.
