Simply put, if more calories are burned than consumed, weight loss will occur. Countless diets exist that complicate this matter, but weight loss is merely a function of the amount of total calories consumed versus the amount of calories expended throughout the day. According the the National Strength and Conditioning Association, the rate at which calories are burned is influenced by each individual's daily energy requirements. This is highly variable and is specific to each individual.
Daily Energy Requirements
Daily energy requirements are measured in kilocalories, which the American College of Sports Medicine defines as the energy required to raise the temperature of water 1 degree Celsius. Each individual's daily energy requirement is influenced by body size, activity level, age and genetics. However, despite these individual differences, all daily energy requirements are a function of resting metabolic rate, the thermic effect of food, and physical activity.
Resting Metabolic Rate
Resting metabolic rate is a measure of the calories needed to perform basic bodily functions, such as respiration, digestion, and cardiac function. According to the National Strength and Conditioning Association, resting metabolic rate accounts for 60 to 75 percent of daily energy expenditure. A higher resting metabolic rate is associated with increased daily energy requirements, and resting metabolic rate is influenced by the amount of lean body tissue you have, increased body temperature and simply being younger.
Thermic Effect of Food
The thermic effect of the food consumed can also influence the body's daily energy requirements. According to the American College of Sports Medicine, the thermic effect of food is the increase in the body's energy expenditure above the resting metabolic rate following a meal. This includes the energy cost of digesting, absorbing, metabolizing and storing food. The National Strength and Conditioning Association asserts that the thermic effect of food accounts for 7 to 10 percent of daily energy requirements.
Physical Activity
According to the National Strength and Conditioning Association, physical activity is the second largest influence on daily energy requirements, right behind resting metabolic rate. The effect of physical activity on daily energy requirements is influenced by the frequency, intensity and duration of exercise. Increases in any or all of these variables will result in an increase in total energy consumed. Further, aerobic activities such as running provide the highest energy cost and will thus have the biggest influence on weight loss.
Weight Loss
Because your resting metabolic rate is largely genetic, weight loss is often more difficult for some people than others. However, the type and amount of food consumed and the frequency, duration and intensity of exercise make weight loss possible for just about anyone within reason. The golden rule of weight loss is to achieve a negative energy balance, that is, to burn more calories than you consume. According to the National Strength and Conditioning Association, a 3,500 kilocalorie deficit will result in a loss of 1 lb. This seems like a lot, which is why a balanced diet and gradual weight loss is highly recommended. The National Strength and Conditioning Association further reports that it is impossible to lose large amounts of weight without also losing lean body mass and thereby risk severe dehydration. Therefore, a weight-loss goal of 1 to 2 lbs. per week and a calorie deficit of no more than 500 to 1,000 kilocalories per day are recommended for healthy weight loss.
References
- "Essentials of Personal Training"; Roger W. Earle and Thomas R. Baechle (eds.); 2004
- "Essentials of Strength and Conditioning"; Thomas R. Baechle and Roger W. Earle (eds.); 2008
- "Resources for the Personal Trainer"; Walter R. Thompson (ed.); 2010
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