For years, people have been perplexed by the sometimes intricate and tedious process of counting calories to lose weight. Figuring out how many calories you should eat a day and how many calories each food item contains may leave you confused. A quick answer to weight loss is to create a calorie deficit in the body through proper nutrition and exercise.
Concept
The concept of a calorie deficit for weight loss is also known as a negative energy balance. What this means is that the body is burning more calories for energy than it is consuming. Conversely, a positive energy balance is when more calories are being ingested and stored than are being used for energy. Energy expenditure occurs when nutrients are broken down to promote muscular contractions and other cellular activities. Energy, in the form of heat, is released from the body. This is why a reference to a person's metabolism is so closely related to the ability to lose weight. Metabolism is the sum of all the energy-releasing processes in the body that can be measured as energy expenditure.
Calculations
Losing 1 lb. of weight requires a reduction of 3,500 calories. The aim in achieving this reduction should not be focused on starvation. Instead, it should involve a systematic and safe reduction process. A safe goal is to aim for reducing intake or increasing expenditure of about 500 calories per day. Ultimately, caloric expenditure is determined by your basal or resting metabolic rate. Essentially, this is the amount of calories the body needs just to exist. The goal is to raise the resting metabolic rate so the body burns more calories while at rest, enhancing weight loss. An important step is determining what is your resting metabolic rate. This can be done by figuring your healthy or desired weight and multiplying that number by 10 (calories per pound). For example, if you weigh 250 lbs. and your desired weight is 220 lbs., you multiply 220 x 10 to get your estimated daily caloric expenditure. To lose weight based on this number, subtract 20 percent of caloric needs for food intake (2,200 - 20 percent equals 2,200 - 440 = 1,760 calories/day).
Thermal Effect of Food
The process of eating or ingesting nutrients can contribute to creating a calorie deficit, as well. This concept is known as the "thermal effect of food." Essentially, it costs the body calories to chew, digest, absorb and store nutrients. This effect depends upon the size of the meal and the type of nutrients involved. For instance, the body spends or expends more energy to convert carbohydrates and proteins, 26 and 24 percent respectively, than it does to store fat--3 percent energy expenditure. Eating a diet rich in complex carbs and lean proteins provides fewer calories than a high-fat diet, and also requires more energy to process these nutrients for use or storage. This creates a negative energy balance which contributes to weight loss.
Physical Activity
Increasing physical activity can significantly raise the calories you burn. According to the Yale University School of Medicine, performing the following activities continuously for 20 minutes contributes to caloric expenditure: walking (4 mph), 140 calories; Tennis, 140 calories; jogging, 160 calories; dancing, 180 calories; and rowing (machine), 120 calories. Resistance training also helps in the development of lean muscle tissue. The more lean muscle you have, the higher your resting metabolic rate will be, and the more calories you burn.
Considerations
Some foods are considered negative calorie foods. They contain fewer calories than it takes to break them down. For example, if you have a stalk of celery that contains approximately 5 to 10 calories, the body could expend 150 calories to break down and digest the celery. This would create a 140 to145 caloric deficit. On the other hand, however, if you were to eat a dessert with 400 calories, that same 150 calories used to digest it would leave a caloric surplus. These calories will be stored as fat.
References
- "American Fitness'" The Positive Attraction to Negative Calorie Foods, George Redmon; Jan./Feb. 2007
- "American Fitness;" Calories In, Calories Out: The Science Behind Weight Loss, John Mego; March/Apr. 2007
- "Sports and Fitness Nutrition;" Robert Wildman and Barry Miller; 2004
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