Friday, March 27, 2009
A Calorie is a Calorie (& a kJ is a kJ)
There has been the spartan Pritikin Diet, the uninspiring low fat diet and the draining low carb diet, all highly successful in book sales, and equally unsuccessful in long-term weight loss. Even the quite sensible CSIRO Total Wellbeing Diet has done little to trim the nation’s waistline, because most people can see only four weeks into the future, not four years.
Weight loss, but not that much
Last month the New England Journal of Medicine published a study in which over 800 adults were placed on four different weight loss diets from the low fat, high protein diet to the low carbohydrate diet. On average, they lost 6 kg after 6 months and 3-4 kg over two years, no matter what type of diet they were on.
Note two things: it is not common for any group to be tracked for this long. Kudos to the researchers. And, as you can see, after the first 6 months the novelty wore off and lost weight gradually returned.
Return to the norm
Interestingly, all the dieters tended towards a similar style of diet. Those on a low carb diet tended to increase their carb intake over time and those on a low fat diet gradually increased fat intake. After two years, 645 adults remained on the diet, only a 20% drop-out rate. More kudos to the researchers as drop out rates from diet studies are often around 30-50%.
The most successful dieters in the study attended regular group sessions and adhered more closely to the advised diet. The authors of the trial, from the Harvard School of Public Health, suggested that it is our behaviour, more than the type of diet, that influences weight loss.
What does it all mean?
People who are selected for scientific trials are chosen because they are most likely to go the distance, in this case two years. What you see here is probably the best possible result for dieting. Not much more than 3kg over two years. Hardly exciting.
As the highly respected Prof Martijn Katan commented: “We do not need another diet trial; we need a change in paradigm”. Agreed. As you have heard me say many times, it is our relationship with our body that is the key. When we decide that our body deserves to be respected and well looked after, then we may see a decline in belt size.
Reference: New England Journal of Medicine 2009; 360: 859-873