Found on RunnersWorld.com and written by Amby Burfoot
New calculator shows that you need to burn more than 3,500 calories.
You’ve probably heard the number-one “rule” of weight loss: It takes a 3,500-calorie deficit between calories consumed and calories burned to produce a one-pound drop in body weight. This old chestnut is more than 50 years old. Problem is, it’s wrong.
Physiologists, nutritionists, and unsuccessful dieters have long regarded the 3,500-calorie-rule with suspicion. But few understood why, and even fewer had a better rule to propose.
Until now. Last week, the National Institutes of Health, with a big assist from weight-change mathematician Kevin Hall, Ph.D., unveiled a weight-loss Body Weight Planner (BWP). It allows you to plot a realistic weight-loss strategy so you can measure your progress according to verified benchmarks rather than the theoretical (and wrong) 3,500-calories rule.
Hall is not a doctor, nutritionist, or exercise scientist. He’s a mathematician who specializes in mathematical modeling. He created the BWP by analyzing the best weight-loss studies, and then by constructing a model that fit the results of these studies.
“There are no magic bullets in our system,” Hall told Runner’s World Newswire. “We built our database from the results of very strict, very well-controlled studies, like those that took place in a metabolic chamber where the researchers could monitor both calories consumed and physical activity. Our aim is to synthesize all the best results into one simple tool.”
The 3,500-calorie rule dates from 1958, when Max Washnofsky, M.D., wrote a paper in the American Journal of Clinical Nutrition concluding “that 3,500 calories is the caloric value of one pound of body weight lost.”
The number was simple, stark, and capable of being reduced to 500 calories/day x seven days a week = 3,500 calories/week, or one pound of weight loss. Result? The 3,500-calorie rule stuck, and prospered. Today, many conventional weight-loss plans still tout the 500-calories-a-day approach.
In fact, the 3,500-calories rule is largely accurate if you’re burning a pound of flesh in a chemistry lab. However, the human body isn’t a lab, where you can isolate and analyze one factor at a time. Rather, the body is an organic whole, and has many reactions to changes in calories, carbohydrates, fats, proteins, metabolism, exercise, and hormones.
When you’re dieting, almost all these interrelated events conspire to lower your daily metabolic rate through a process known as “metabolic adaptation.” As a result, a daily deficit of 500 calories produces slightly less effect on each subsequent day. The difference isn’t big at first, but grows substantially with longer periods of time, producing just 50 percent of the expected weight loss over 12 months.
“The biggest flaw with the 500-calorie-rule is that it assumes weight loss will continue in a linear fashion over time,” says Hall. “That’s not the way the body responds. The body is a very dynamic system, and a change in one part of the system always produces changes in other parts.”
What’s realistic? According to Hall, in the first year of a new weight-loss program, most overweight people will lose about half the weight that the 3,500-calories rule predicts. In other words, over 12 months, the new rule is 7,000 calories = one pound. (The math changes slightly over shorter and longer periods of time, with few managing to lose weight beyond 12 months.)
That sounds like a bitter pill unless you believe it’s better to succeed with an evidence-based strategy than to fall short with the old, difficult-to-achieve model.
“I suppose some people will be bummed out,” Hall says. “But we believe it’s better to have an accurate assessment of what you might lose. That way you don’t feel like a failure if you don’t reach your goal.”
The BWP allows you to pick your current weight, a target weight, and your timeframe for losing weight. It then calculates the changes you will need to make—lower calorie intake and increased physical activity—to reach your target. The free BWP connects to the NIH’s free “Supertracker,” which provides access to a food database, an exercise log, and other health tools.
The BWP doesn’t let you select a given calorie deficit, such as 500 calories a day, and see where it will leave you after a set amount of time. However, Hall’s 7,000-calorie rule of thumb works for many overweight individuals over one year and shorter. For example, cutting 500 calories a day for 180 days will give you a total deficit of 90,000 calories. Divide by 7,000, and you obtain a weight-loss goal of 13 pounds.
Individual weight losses are highly variable. The most overweight people will lose the most weight in the first months of their program; the leanest will lose the least. That’s also why the “last five pounds” is always the toughest. Once you get leaner, it’s more difficult to lose additional weight.
The Pennington Biomedical Research Center hosts a different online weight-loss predictor. It allows you to input a daily calorie deficit. It produces results similar to Hall’s DWP, but is even more stingy when it comes to assessing realistic weight loss.