'Healthy' diet = weight gain

Part 2: Low-calorie, weight loss diets don't work

As diet gurus and nutritionists have recommended low-fat diets for weight loss for decades, you might expect that there are lots of studies to support them. There isn't. Even today, I can still find no study which clearly shows that low-fat diets result in long-term, significant weight loss among the chronically obese. In fact, most such studies show marginal improvements in weight at best, and some actually show significant weight gain among test subjects.

Let's look at a typical study: a two-year study of 171 women on a low-fat, weight loss diet. After 6 months, they had achieved a maximum weight loss of only about seven-and-a-half pounds, which isn't exactly earth-shattering; and by year two some of that weight was regained. In a study such as this, not everyone will lose (or gain) the same amount; the average figure is a 'plus or minus' amount. This is the 'deviation'. A significant point of this study was that the standard deviation was more than twice the average weight loss. What this tells us is that many of the people in the study actually gained weight on the low-fat diet.[1]

This might come as a surprise to you, but it will not be a surprise to those who have studied the literature. The fact is that not one clinical study has ever shown that low-fat diets results in long-term reversal of obesity in most subjects, whether it is combined with exercise or not. Indeed, over the past 20 or more years, fat consumption has consistently gone down - and national rates of obesity have gone up at precisely the same time. Let's compare the figures for the USA for the periods 1976-80 and 1988-91:

• Average fat intake fell 11%.
• Average calorie intake decreased from 1,854 kcal to 1,785 kcal
• Percentage of population consuming low-calorie products rose from 19% to 76%.
• Overweight increased 31%.

This doesn't mean that the one necessarily caused the other; however, with no change in the proportion of people with a sedentary lifestyle, the authors of this study conclude that it is:

'Reduced fat and calorie intake and frequent use of low-calorie food products' that are responsible for the 'paradoxical increase in the prevalence of obesity'.[2]

There is no reason to suppose the trends in the UK are any different. If you know of any scientific study that does support a low-fat diet as an effective weight-loss diet, please email me.

References

1. Sheppard L, et al. Weight Loss In Women Participating in a Randomized Trial of Low-Fat Diets. Am J Clin Nutr 1991; 54: 821-8.

2. Heini AF, Weinsier RL. Divergent trends in obesity and fat intake patterns: the American paradox. Am J Med 1997; 102: 259-64.