For weight loss, many practitioners take the energy balance approach. It's commonly recommended to increase energy (calorie) expenditure and decrease energy (calorie) intake so the body uses stored energy (body fat) to provide the energy that is needed, but not immediately available from food, resulting in a negative energy balance. Since one pound of body fat stores approximately 3,500 calories, it takes a 3,500-calorie deficit to achieve an average weight loss of one pound of body weight. And a 3,500-calorie negative calorie balance could be achieved in one week by:
• Cutting calorie intake by 500 calories per day (7 days x 500 calories = 3,500 calories),
• Increasing physical activity by 500 calories per day, or
• Cutting calorie intake by 250 calories per day and increasing physical activity by 250 calories per day.
Sounds pretty simple, right? Many people argue that it's not that simple and that when people of varying weights, diets, and exercise habits try to change their weight by eating 3,500 fewer calories (or burning them off exercising) it doesn't always result in a pound of weight loss. To address this, researchers at the National Institutes of Health have developed a computer simulation that accounts for metabolic changes among different people to more accurately predict how body weight will change and how long it will likely take to reach weight goals. The online tool simulates how factors such as diet and exercise can alter metabolism over time and lead to changes in weight and body fat.
To test the model, researchers compared predicted weight changes to actual changes in people - of differing genders, ages, heights, and weights. They found that people's bodies adapt slowly to changes in dietary intake. They also found that heavier people can expect greater weight change with the same change in diet, though reaching a stable body weight will take them longer than people with less fat.
Practitioners may find this tool helpful in assisting people with setting realistic goals for amounts of weight to be lost in a given time period as well as determining the changes in eating (calories) and exercise that are required to achieve and maintain a certain goal weight. The researchers who developed this tool emphasize, however, that the tool is for research/clinical use only and is not intended to provide personal medical advice or substitute for the advice of a physician or weight management professional. In fact, the program can run simulations for changes in calories and exercise that would not be recommended for healthy weight loss.
Check it out: http://bwsimulator.niddk.nih.gov/ and let us know what you think!