The American Society for Nutrition published a “consensus statement” in the American Journal of Clinical Nutrition that challenged the common notion that one could lose weight simply by measuring calories burned versus calories eaten – the kind of thinking that says “I can eat a cheeseburger this morning if I run an extra 2 miles this evening.” According to these health experts, that’s all poppycock.
For one, they say, the kinds of foods you eat and how you eat them play a big part in whether you gain or lose weight. Two foods with the same caloric value, in other words, may have a very different impact on your weight.
On the other side of the equation, people burn calories in many different ways, some more effective at weight loss that others. Even when 2 people follow the same exercise regimen, they will see very different results. People are even know to gain weight when they increase exercise (usually because the exercise makes them hungrier).
And then they challenge the timescale involved. Many people think “OK, if I cut 1000 calories a day for a week, and burn an extra 1000 calories in that same week through exercise, I’ll be rid of 14,000 calories at week’s end.”
First the time scale is too short, habits need to change over a long period of time be effective. ” When a given day’s intake and expenditure are plotted against each other, there is little association. It is only when they are averaged over much longer periods (weeks) that there begins to be a balance struck between intake and expenditure.”
Then you continue…
“And if I lose 14,000 calories, with 3500 calories equalling one pound, I will lost 4 pounds this week.”
The problem there is that, at least among the medical professionals who signed the consensus statement, is that the 3500 calories equals 1 pound generalization is apparently not based on fact.
C. “It takes a reduction of 3500 kcal (15,000 kJ) of energy intake to lose 1 lb of body weight.”
The origin of the “3500 kcal per pound” rule is based on the calculated energy content of body weight change and is often misapplied to predict the weight-change time course after a given intervention (19). This is a fundamental error because no time period is speciﬁed for that intervention. The impression is given that even a temporary intervention will therefore result in a permanent body weight change. Furthermore, the erroneous application of the rule to predict the impact of a permanent intervention gives the impression that a linear change in body weight is expected over protracted periods of time, which is known to be untrue. Rather, even when perfect adherence to an intervention with no active compensation is assumed, it is generally acknowledged that weight change will slow over time due to passive compensatory changes in energy expenditure that occur with the weight change. Therefore, the panel recommended that the 3500 kcal per pound rule should no longer be used.
So forget about it.
What, then, do they recommend?
Easy – small changes. Even a tiny change like adding lettuce to your diet, or having one less soda each day, or walking to the store on occasion, can have unpredictable effects. The whole system of food intake, exercise and weight loss or weight gain is highly complex, and even tiny changes can have big effects (for better or worse).
In the statement’s words:
Any imbalance between the intake and utilization of… macronutrients will lead to an alteration in body composition. The energy stored per unit body weight of carbohydrate, fat, and protein varies considerably, especially when accounting for the associated intracellular water.
So you toss the weigh tloss calculator, at least for now.