Wednesday, January 04, 2006

JAMA: Low-Fat Diets No Better than High-Fat

If the findings of the most recent long-term study investigating the efficacy of low-fat diets are true, you can expect nothing more than weight maintenance as the result of your deprivation. Heck, you won't do any better or worse than those who do nothing to alter their diet if your weight is what you're looking to change.

I'm not a researcher, nor do I pretend to be an expert about study design or statistics. What I do know is how to do math and the simple adding and subtracting of the numbers in this study prove that a low-fat diet does not help you lose significant, appreciable weight over the long-term. It may, in fact, even increase your risk of heart disease and diabetes when waistline and waist-hip ratio changes are considered.

Researchers recruited a very large number of women, from diverse backgrounds who were all post-menopausal. They randomly established two groups - one group was given specific instruction, group and individual counseling and support to reduce the fat in their diet; the other group received only a pamplet with diet-related materials.

There were some differences in the groups - these were not statistically significant, but are worth noting.

In group 1, the average weight was 168.96-pounds at the start, the women averaged 5'3" with a BMI of 29.1 and the average age was 62.3. At the start of the study, the average woman in this group consumed 1788.1-calories per day. This group was the "intervention group" that received intense education and support.

In group 2, the average weight was 168.74-pounds at the start, the women averaged 5'3" with a BMI of 29.1 and again, the average age was 62.3. At the start of the study, the average woman in this group consumed 1789.2-calories per day. This group was the "control group" that received only diet-related print materials at the start.

At the end of the study, the intervention group weighed, on average, 166.54-pounds - a reduction of 2.42-pounds; the control group weighed, on average, 167.42-pounds - a reduction of 1.32-pounds. So, the intervention group lost just 1.1-pounds more in seven years than the group that was given no support to specifically alter their diet.

Where things get interesting is when you look at how calorie intake differed between the groups.

Group 1 ate 1788.1-calories at the start and just 1445.9-calories at the end. Group 1 reduced their calorie intake by 342.2-calories a day.

Group 2 ate 1789.2-calories at the start and just 1564.0-calories at the end. Group 2 reduced their calorie intake by 225.2-calories a day.

But, let's be up front about this - weight loss was not a goal of either group nor was a reduction in calorie intake. It happened though and it should be discussed since we're repeatedly told if you reduce calories and increase activity you will lose weight. And not just a couple of pounds, but significant amounts of weight if you adopt your dietary changes and eat a low-fat diet as your way of eating.

As this study gets mulled over more, one explanation is going to be put forth - these women experienced a normal decline in their metabolism as they aged in the study and did not need as many calories to maintain their weight. Guess what? That's true. But, what is also true is that both groups of women were eating a calorie load that should have resulted in weight loss - they were eating less calories each day than they needed to support their weight.

If you recall, at the start of the study, both groups averaged the same age and height. Based on these numbers with the average weight at the start, the average calorie requirement to maintain weight - Active Metabolic Rate (AMR) - for the groups was 1854.2-calories each day. They were already consuming less calories than this on average and were still overweight with an average BMI of 29.1.

At the end of the study, the women participating had aged 7.5-years and should have indeed had a slight metabolic decline to maintain their weight - their AMR would be 1810.5-calories each day to maintain their weight.

But, both groups were eating significantly less calories than their AMR and still maintained their weight! Here's the kicker - both groups also increased their activity level from the start of the study too! So, they were eating less and were more active and still didn't lose any appreciable weight!

What happened to "eat less and move more" and you'll lose weight?

What happened that the intervention group, eating 118-calories LESS each day than the control group, didn't lose any more real weight than the control group?

They reduced their calories, reduced their fat in real grams and as a percentage of their calories and for what? A pound more than the group that ate more over the seven years?

Quite frankly a weight loss of just 2.42-pounds over seven years, with such a restriction of calories, is a dismal result for low-fat diets. More important though is that this group actually increased their waistline and waist-hip ratio (WHR) over the period of seven years even with the very miniscule weight loss. That is a danger sign - the dietary approach had a negative effect on a specific health marker - an increase in WHR places one at an increased risk of heart disease and diabetes!

Why the researchers are claiming this as a victory for low-fat diets is beyond me. If I were a participant in this study, I'd be angry. I'd be angry my health was put at risk and that my efforts for seven long years were for nothing more than a pound. I'd be looking at the women over in the control group who got to eat as they wished and want to know why my low-fat diet didn't work better than their diet, how they got to eat 38% of their calories from fat when I was made to keep mine below 30%, how they got to eat more calories...all the while my WRH increased along with my risk for heart disease and diabetes!

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