I am sure by now that you all realize that most of the work I do involves weight management counseling. I absolutely cringe when a new client asks “how much weight will I lose by my vacation, my classreunion, my wedding, my daughter/son’s wedding “ or just fill in the blank. Years of continued education and experience have reinforced my standard response: it all depends.

There are just so many factors that play into this equation: age, gender, body composition, fitness level, willingness to exercise (how much, how often, how long), what you are willing to moderate (portion size, alcohol, take-out/delivery/fast food), home-cooked meals vs restaurant, religious/ethnic/cultural food considerations, foods that you can’t live without, etc.

So I base my recommendations on the textbook fact that to lose 1# of body fat you need cut or spend 3500 calories each week; 7000 calories to lose 2# each week. No matter how much weight you have to lose it is not considered safe to lose more than 2# per week. I have many clients who are extremely compliant with my recommendations, but there is just no predicting how much weight, if any, they will lose from month-t0-month. Maybe this is you?

Now I know why. It seems that the math is all wrong. The rule of 3,500 calories is a myth.

Back in 1958, after a rigorous review of available research and the use of a bomb calorimeter, a scientist by the name of Max Wishnofsky assigned the caloric value of 9.5 calories per gram of adipose (body fat). But he assumed that all weight loss would be only fat and at a consistent rate. Prior to 1958, any knowledge about how humans lost or gained weight was from observations during periods of famine or chronic wasting illnesses.

In the subsequent fifty-plus years we have learned much about how body composition changes but not so much about the rate of change. And so the health care provider continues to quote ” 3,500 calories”. There have been several papers addressing this inaccuracy, with the most recent a 2014 Research Commentary in the Journal of the Academy of Nutrition and Dietetics. While newer predictive equations have been developed, they lack the stringent testing that results in the validity required in the clinical setting.

For now though you can still lose weight by creating a calorie deficit through healthy eating and physical activity. How quickly? It all depends.