If fiction is authoritative, from a respected source, is quoted and re-quoted and is a handy and useful fact, it can have a very long life. This is in spite of being passed on by many competent professionals. I have been assuming it was a fact that if we burn off, or reduce our intake, by about 3,500 calories, over whatever time interval that takes, we will lose one pound of weight. This now-found-to-be erroneous factoid has been around for 57 years. I learned it in undergraduate school and have been using confidently for decades. It is not a shock that later, better science finds a more accurate and nuanced approach to estimating weight loss from calorie reduction. Science is supposed to keep improving our understanding all the time. What is rather shocking is how long it has taken, and how widespread the use of the error has become.

The people who uncovered the errors, published their article in June 2014in the Journal of the Academy of Nutrition and Dietetics. Their title is Time to Correctly Predict the Amount of Weight Loss with Dieting. At first I thought the article was something that could be skipped over for a while, because of the complexity of the issue. Moreover, the authors cautiously added (as scientific writers are taught to do) solemn statements about the need for “far more research.” This research is needed to improve model terms; to supply more accurate empirical calculations; and to better understand the dose-dependent influence of exercise; and lastly the impact of weight changes in the presence of disease.

So it is much more complex than the old “3500 calories gets you one pound.” Despite this complexity, let me try to get to the heart of this issue. Dietitians and nutritionists have for decades used a number, 3500 calories, to predict how much weight you will lose for every deficit of 3500 calories. We’ve been taught since Max Wishnofsky MD a medical researcher, reported in 1958 that “What is the caloric equivalent of one pound of body weight gained or lost?” He concluded, “An energy deficit of approximately 3,500 calories are needed to lose 1 lb of body weight.” He did this 57 years ago and thousands of citations in the scientific literature have repeated it. Like most dietitians, I’ve used the number many times myself to predict weight gain or loss. I’m definitely not alone. Diana M. Thomas, PhD, et.al, who wrote the article cited above, said in the article, that the 2006 Modern Nutrition in Health and Disease, a commonly accepted authoritative and definitive textbook in nutrition also quotes the Wishnofsky number – 3500. In addition, Mayo Clinic, Livestrong, and countless other websites and publications use the same number.

The problem is that no matter how many of us keep repeating this number, the number that we were taught in undergraduate and grad school, does not make it true, or make it work. Unfortunately it is not an accurate number in the face of what we know now.

There are quite a few mistakes in the assumptions Wishnofsky used to calculate the 3500. One small part of the problem is that his number is based upon the burning of fat; unfortunately, when we lose fat we also lose some lean tissue. In addition, as we begin cutting calories from our diet, our bodies react by slowing our metabolism. That makes it harder to lose weight as we become lighter. It’s a really sad reality that as we lose weight, our bodies work diligently to defend our weight. Above all, as our ancient ancestors had to do, a body must defend against starvation. And the distressing fact is that our bodies defend our weight even when we weigh way too much. Ouch!!!

Also, there are complex metabolic adaptations going on when people are losing weight over time. You can read the details of the list of the many variations in the numerous phases of energy restriction in the article linked above. The bottom line is that we vary in a big way as individuals.

A number of newer models have been developed to predict weight loss. They involve complex thermodynamics and chemistry laws and use sophisticated applied mathematical models. They are all far more complex than the simple 3500-calorie – based model developed by Wishnofsky. It seems that the only answer it to turn to the development of new apps on computers and mobile devices that can be used to help patients predict what to expect from calorie restriction and exercise.

The above problem is an especially poignant issue for someone like me. I’ve invested in 9 years of formal education, including two graduate degrees and countless thousands of hours of continuing education and reading scientific research. It so frustrating for me because it’s difficult enough for the general public to be able to discern fact from fiction in the world of nutrition, where there are so many popular fads. With a few oversimplified or even fake numbers, and with a testimonial or two, whether made up or purchased from a willing celebrity, these many sources of misinformation seem to speak to the public in loud voices. Professionals in the field, well practiced in the relatively easy use of the 3500 number, will have to redouble our educational efforts.

The reason that I decided to address the issue this year is that numerous writers are addressing it and I’m afraid many people, seeing the additional complexity, may just want to give up. Giving up is not going to solve the over weight/obesity problem and associated health problems. People can lose weight and people do lose weight; and yes, some maintain their weight loss. So I thought that if I wrote a few facts that could support weight loss goals, maybe it would be a benefit to someone who might get discouraged.

• If you want to try one of the newer applications, you may want to start with the National Institutes of Health (NIH) Body Weight Planner. It gives a more accurate weight loss prediction than using calculations with 3500.
• If you also want some help with food amounts and choices you may like the Supertracker from USDA (United States Department of Agriculture)
• The nice thing about both the Body Weight Planner and the Supertracker is that they both include physical exercise and food information. Both are part of the equation for weight gain or loss.
• One of the best ways to keep your metabolism high while losing weight is to exercise. It protects and builds muscle mass, which enables your metabolism to burn up more calories.
• Remember that fluctuations of water in the body can mask weight loss. If your efforts don’t seem to be working because of water, it will likely be harder to stay motivated. When we exercise more than we’re used to exercising, we may have some edema; (fluid around the microscopic tears in the muscle), water weighs something. So you may wonder if you initially gain weight when you exercise, but stop worrying. It’s not real (from fat) body weight. Retaining too much water adds weight to the scale, but it will go away. Also, dehydrating loses more weight, but it will come back.
• Weight on the scale is not the ultimate goal. A healthy amount of body fat is the goal. So be careful that you’re not losing weight too quickly (losing a load of body fluids) and then gaining that right back. Losing and gaining it back has been shown by some researchers to be a fairly reliable way to lower your metabolic rate. (Ultimately you have to live on fewer and fewer calories.)
• Changing your eating and exercising habits is key; it’s clearly an effective and long-term choice to sustain a lower weight. Losing weight on a very low calorie diet does not help you learn how to eat to sustain your new lower weight. (I’m thinking especially of the diets that send little pre-made meals in the mail or drinking special shakes to lose weight rapidly.) What do you learn about developing new eating habits while losing weight? Not much. Even if you think, “To maintain my weight loss, I can eat what came in the little packages,” remember, the special meals are often made with ‘special’ low-calorie ingredients that are not found in your kitchen. Your homemade or restaurant made lasagna, mac and cheese, pizza and so on are not made with a load of some cheap zero-calorie fiber like inulin, but the food packet may be, for example.

The 3500-calorie assumption was only a rule of thumb; using scientific assumptions that did not account for individual differences or the body’s adaptations to hunger, exercise, and other areas, now understood better. It is clearly only right occasionally, in some personal circumstances, but for most people, it is not accurate. I take comfort in thinking that as a rule of thumb, my use of it may have helped more people than hurt them. After all, if they were determined to deficit calories, through exercise or through cutting them out of one’s diet; ultimately, they gained more control over their weight. It is obvious from bariatric surgery that if you restrict your stomach so it artificially can’t contain as many food calories (as much food), you will lose weight. There is a scientific equation, with adjustments for you as an individual that fits your individual profile. Weight loss and calorie reduction are truly related. It just isn’t for each person the simple equation: 1 (lb weight loss) = c (calories reduced) / (divided by) 3500.

But while you’re waiting for the latest and greatest software applications to be developed, using a more complex and individualized equation, you can work with the fairly good NIH and USDA calculators to help you predict weight loss. One other possibility is not to worry too much about how much you’ll lose in a given period, but try keeping your focus on continually altering your eating and exercise until you’re at a healthier weight. It can be done.