Walk into almost any supermarket and you will be assaulted by products that overtly state or subtly imply that they will help you lose weight or prevent you gaining weight or help you lose the weight you are gaining… I think you get the idea. The variety is sometimes impressive but they usually fall into one of three broad categories, low fat (98% Fat FREE!) low carb, and no added sugar/sugar free. The first two in this list depend upon the idea of macro-nutrients or that it matters in what form the energy you get get from food comes in. In other words eating less fat is better for you even while the the amount of energy (kJ) you may receive stays the same, ditto with carbohydrates. In this way we might be tempted into thinking that it is really what we eat and not strictly the energy content of our diet that makes the difference.
Those sceptical of these sorts of diets have long pointed out that it is the energy in vs energy out (via exercise) that is the determining factor in weight management. This picture is complicated by the recent discovery of how an individual’s bacterial flora affects the available energy in the food they eat but in essence the argument remains the same. Those that subscribe to this view got an additional boost in credibility from a study published recently that compared various diets long term and gauged the differences seen in weight loss after 2 years.
In the study 811 overweight adults were randomly assigned to one of four diets, each diet varied the number of calories received from fat, protein and carbohydrates. Participants were provided with daily meal plans and had regular meetings and recorded their food intake in a diary. Those in the study were also encouraged to engage in 90 minutes of moderate exercise a week. The results? No difference in weight loss. In fact the best predictor of weight loss was adherence to the program and not which diet was assigned. All groups lost the most weight in the first 6 months and started slowly regaining weight after 12 months. It seems the message is this: Advertising gimmicks are just that and the nutritional information that really matters for weight loss is the kJ content of the food.