Calculating Caloric Needs
BASAL METABOLIC RATE
Calculating your caloric needs is in part based on you Basal Metabolic Rate is the amount of energy (calories) needed to keep a person alive. That includes a person’s heart beat, lungs movements, brain function, tissue processes, and body temperature. When a person exerts themselves beyond these basic measures energy expenditure increases. Even intensely exercising for a short amount of time can increase caloric needs. The quantity and quality of food you eat, water you consume, and heat your body produces all affect your BMR.
Factors that affect BMR:
The body’s size and shape: the ratio of body surface area to body volume influences metabolic rate because the greater the surface area, the greater the amount of heat is lost. Tall and slender people, compared to short and stout people, will lose more body heat and therefore require more energy to maintain body temperature.
Lean muscle and fat tissue composition: Muscles use energy faster than fat cells, even when not in use. The more muscle a person has, the more energy they need to keep their muscles alive.
Male or Female? Women have more body fat and less muscle than men. Women’s BMR’s are 5-10% lower than men’s.
Age: The older a person is the less muscle they tend to have. Due to both natural degeneration and a decline in physical activity, the elderly have lower BMR’s.
Stress: Physical or emotional stress induces the body’s “fight or flight” response and therefore increases a person’s BMR dramatically. The longer a person is stressed, the more fatigued they become. Overly stressed individuals are very vulnerable to infections and other illnesses.
Growth Rate: During growth, our cells need extra energy. Children need more energy from conception until they are late teenagers. Then growth slows down and people need fewer calories to sustain themselves.
Ambient temperature: People living in warm climates need less energy to maintain body temperature than people living in cold climates.
Drugs, especially stimulants like caffeine, nicotine, or amphetamines: People find that they gain weight when they quit smoking in part because their metabolism’s are slowing down.
Illness: Infections increase metabolic rate because the body is trying to fight off the disease. Immune cells seek out and attack the disease. A fever emerges as the body tries to destroy the infectious pathogens.
Resource: Murray, M. (2000) Dr. Murray’s Total Body Tune-Up. Bantam Books. New York.
How Do I Find My BMR?
Men: weight in lbs/2.2 = hourly BMR x 24 = daily BMR
Women: (weight in lbs/2.2) x.9 = hourly BMR x 24 = daily BMR
OR:
Women= (weight in lbs x 10) ± 10% depending if you have a big(+10%) or small (-10%) bone structure (determined by measuring wrist with thumb and middle finger). If you barely touch, you are big boned-add 10%; if your fingers go past each other you are small boned-subtract 10%.
Men= (weight in lbs x 11) ± 10% depending if you have a big(+10%) or small (-10%) bone structure (determined by measuring wrist with thumb and middle finger). If you barely touch, you are big boned-add 10%; if your fingers go past each other, you are small boned-subtract 10%.
Once you have calculated your BMR, you will need to calculate your activity level and add the two numbers together in order to get your total energy expenditure.
The Harris Benedict Equation is a formula that uses your BMR and activity level to determine daily energy expenditure. This equation is helpful for most, but is not completely accurate for individuals with lean body mass (muscle). Muscle burns calories and people who have more muscle mass use more calories at rest. If you are very muscular, this formula will underestimate your caloric needs.
Sedentary (little or no exercise) = BMR x 1.2
Lightly active (light exercise/sports 1-3 days per week) = BMR x 1.37
Moderately active (moderate exercise/sports 3-5 days per week) = BMR x 1.5
Very active (hard exercise/sports 6-7 days a week) = BMR x 1.72
Extra active (very hard exercise/sports & physical job or 2x training) = BMR x 1.9
If you are trying to lose weight, I suggest consuming 500 calories less per day in order to lose 1 lb a week. Or, you could eat 200 calories less per day and expend 300 more calories exercising to result in a 500 calorie deficit.
Discovering your caloric needs is important for weight management, but it is not the only thing that matters. The quality of foods you eat and the proportions of macronutrients are also important factors to consider. If you do not know what your macronutrient distribution should be, email me and set up a free phone consultation today!
Tags: basal metabolic rate, Caloric needs, energy expenditure
