How to Use Your Metabolic Rate to Establish Calorie Needs

You may have heard that 3,500 calories is equal to a pound of body weight — so, the less you eat, the more you’ll lose. By reevaluating your meal plan and your goals to make sure they’re realistic, and making small tweaks to your meal plan instead of an overhaul, you can stay on the healthy weight loss straight and narrow.

Plateaus are natural and occur because once you’ve been losing weight for a while, you need to change up your routine. As you lose weight, your metabolism slows, you require fewer calories, you might be losing that oh-so-beneficial muscle mass, and so on. Whatever its cause, remember that a plateau is your body’s way of telling you that your metabolism needs a little boost.

Back to that number of 3,500 calories per pound: Although not entirely clear cut, the number is a decent estimation to go by to calculate the nutrients you need. Because a week has 7 days, to lose 1 pound per week, you’d need to cut out 500 calories per day. Want to lose 2 pounds per week? Cut out 1,000 calories per day.

Want to lose 3 pounds per week? Stop right there. A healthy rate of weight loss is 1–2 pounds (0.5–1 kg) per week. Anything greater than that, and you run the risk of adaptive thermogenesis — a significant slowing of your metabolism, loss of muscle mass, and risk for nutrient deficiencies.

To make sure you’re getting enough calories but not too many, take your total energy expenditure and subtract about 500–1,000 calories either by eating that much less per day or adding that many to your burn through exercise. For example, let’s say you’re typically lightly active, and your burn rate is 1,900 calories. You need to do one of the following:

  • Increase your activity level on top of what you are already doing day-to-day

  • Eat 1,200–1,400 calories per day

  • Combine both ways, such as eating 1,500 calories per day and burning an additional 200 through exercise.

Here are the minimum daily calories your body needs at rest to fuel your organs and muscles, according to the American College for Sports Medicine:

  • 1,200 calories for women

  • 1,800 calories for men

These are the absolute minimum calories you should be consuming. If you have more muscle or very active, you need to add more to the baseline. How much more? Basically, you shouldn’t exceed a total deficit greater than 1,000 calories.

If you eat 1,900 calories, but have a burn of 2,900 calories throughout the day from your RMR plus additional exercise, that would correlate to a –1000 calorie deficit, which is the maximum recommended for healthy weight loss.

The magic number that will work for you may be discovered through trial and error. Some research shows that cutting just 100 calories per day from what you typically eat can have a great effect on health and weight. Your magic number will change as your body changes. (Well, it’s not really magic, it’s science.)

In 2012, researchers at the National Institute of Diabetes and Digestive and Kidney Diseases created an online tool that predicts how your body composition will change depending on changes in your diet and activity level. It calculates the number of calories you need during weight loss and maintenance phases.

You can also enter when you changed your calorie intake and get a prediction for when you’ll reach your goal weight. It’s a great reminder right off the bat that your needs will evolve throughout the process.

These researchers found that body reaction time was very slow for weight change and that it took three years for someone losing weight to reach their steady or maintenance state. Don’t let this discourage you. You can still take steps so that you look and feel your best for the short term, but realize you are doing so to improve your lifestyle for the long term.

Don’t feel like doing any equations or younger than 18 years old? The following gives you an idea of the calories you need every day for weight maintenance. If you’re older than 18, for 1 pound per week weight gain, add 500 calories per day and 1 pound per week weight loss, subtract 500 calories per day.

For people under age 18 years, because you’re still growing and developing, it’s important that you consult with your physician before starting in with any weight loss plan.

Estimated Calorie Needs
Sex Age (years) Sedentary Moderately Active Active
M/F 2–3 1,000 1,000–1,400 1,000–1,400
F 4–8 1,200–1,400 1,400–1,600 1,400–1,800
9–13 1,400–1,600 1,600–2,000 1,800–2,200
14–18 1,800 2,000 2,400
19–30 1,800–2,000 2,000–2,200 2,400
31–50 1,800 2,000 2,200
51+ 1,600 1,800 2,000–2,200
M 4–8 1,200–1,400 1,400–1,600 1,600–1,800
9–13 1,600–2,000 1,800–2,200 2,000–2,600
14–18 2,000–2,400 2,400–2,800 2,800–3,200
19–30 2,400–2,600 2,600–2,800 3,000
31–50 2,200–2,400 2,400–2,600 2,800–3,000
51+ 2,000–2,200 2,200–2,400 2,400–2,800

Source: HHS/USDA Dietary Guidelines for Americans 2010. Calorie levels are rounded to the nearest 200 mark.

The table doesn’t take into account females who are pregnant or lactating. Add 300 calories per day in the second and third trimesters of pregnancy, and 500 calories per day during lactation to these numbers.

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