The old rule was that to lose a pound, you must eat 3,500 fewer calories, or burn them off with exercise. But that rule doesn’t work, according to a new study published in Lancet, because it fails to take into account changes in the body’s metabolism as eating and workout habits changes. What more, the effects of dieting on metabolism can vary according to people’s age, starting weight, height and other factors, reports a research team lead by Dr. Kevin Hall of the National Institute of Diabetes and Digestive and Kidney Disease.
As a result, the 3,500-calorie rule can lead to unrealistic expectations and sabotage weight loss. Instead, Dr. Hall and scientists from the World Health Organization, Columbia University and Harvard School of Public Health have developed a simplified, web-based formula they say can more accurately predict weight loss over time. To test its accuracy, the researchers compared predicted weight changes to actual changes in a group of dieters. Here’s a look at the new formula and how you can use it to slim down.
What is the simplified formula? For every pound you want to shed, permanently trim 10 calories a day from your intake. At that rate, according to the researchers, it will take an average overweight adult about a year to achieve half of the desired weight loss. After three years of following this formula, the average dieter will have shed 95 percent of the unwanted pounds. That means that cutting 300 calories a day will eventually lead to a 30 pound weight loss, but it take a typical overweight person three years to lose 28.5 of the pounds.
What’s the science behind the formula? The researchers found that people’s bodies adapt slowly to changes in dietary intake. It’s part of a growing body of evidence that metabolism can change significantly after you start to drop pounds and rev up your workouts. “This research helps us understand why one person may lose weight faster or slower than another, even when they eat the same diet and do the same exercise,” Dr. Hall says. “Our computer simulations can then be used to help design personalized weight management programs to address individual needs and goals.”
How can I personalize the new formula? For a quick, personalized calculation of how many calories you should eat to reach your goal that takes your sex, age, height, starting weight and current activity level into account, you can use the actual tool developed in the study by going to: http://bwsimulator.niddk.nih.gov/, You’ll also be asked to enter your goal weight, how days you play to take to achieve that weight, and how much you’ll plan to increase your activity level. The tool then figures out how many calories to eat, graphs your predicted weight loss if you follow that diet and exercise plan, and calculates what diet you’ll need to maintain the loss, once you reach your goal weight.
Is there any downside to using this tool? Since the online simulator just does math, it’s not intended to replace medical advice from your doctor. It’s possible to run calculations for an extreme crash diet or drastic increase in exercise that could be harmful to your health. Therefore, you also need to use common sense in setting realistic weight loss goals to shed weight slowly, by eating a healthy diet that’s rich in fruits and vegetables. Select an exercise plan that’s appropriate for your age and fitness level, which could be as simple as walking briskly 15 minutes a day, then increasing your speed and distance as your body gets stronger.