Low carb vs. low fat
If weight loss were a sprint, low-carb dieting would win, hands down.
Four recent studies have shown that at the six-month mark, low-carb
dieters lose, on average, about 9–13 more pounds than those on
a low-fat plan. But two studies have now shown that for weight loss,
the two diets end up in a statistical tie after a year. In the first
one, published in 2003 in the New England Journal of Medicine (NEJM),
low-carb dieters spurted ahead of their low-fat counterparts during
the first six months, only to regain pounds in the next six. In the
second study, published in early 2004 in the Annals of Internal
Medicine, the low-carb group kept off the pounds lost during the
first six months, but the low-fat group caught up with them by continuing
to lose weight. In the weight-loss race, low carb seems to be the hare
and low fat, the tortoise.
But it’s more complicated than that familiar fable with its moral
that “slow and steady wins the race.” The numbers of pounds
being lost are relatively modest. The people in the Annals study
were heavy to begin with: The average starting weight was about 288 pounds.
After a year, the low-carb group (including the dropouts) had lost an
average of 11.2 pounds and the low-fat group, just 6.8 (the difference
between them didn’t meet the test for statistical significance).
The people in the NEJM study weren’t as heavy —they
averaged about 215 pounds — but the results were pretty similar.
However, heaviness is a lifelong issue for most people who are overweight
or obese, and losing even just a few pounds may be a bigger victory than
One of the chief objections to low-carb dieting has been that it would
ratchet up levels of “bad” LDL cholesterol by encouraging
people to eat food with higher saturated fat content. But both yearlong
studies found that low-carb and low-fat diets had the same effect on
LDL levels. And low-carb diets outdid low-fat diets with respect to other
blood fats related to heart disease. Triglyceride levels fell further
and the HDL results were better. In the Annals study, the low-carb
diet was better for blood sugar control for people with diabetes.
Averages can be good summaries, but behind them there can be a lot of variation.
Dr. Samaha says someone in the low-fat group in his study lost 79 pounds — and
that person was among the 34% who dropped out of the study. At the other
extreme, another person gained 31 pounds sticking with the low-fat
diet program. There was a huge range among the low-carb dieters, too: from
65 pounds lost to 18 pounds gained.First, low-carb dieting can’t
live up to the hype (what could?) but it has some merit. You can improve
upon it by sticking with polyunsaturated and monounsaturated fats as your
fats and whole grains as your carbs. Second, diets have differing effects
on cholesterol levels and metabolic factors. If you’re serious about
losing weight, you should talk to your doctor about getting a cholesterol
test. The results may help you choose the best diet for you. Third, for
reasons of taste, upbringing, genetics, and other factors, the individual
response to diets varies tremendously. Experiment. See what works for you.
And by all means, get some exercise, too.
September 2004 Update
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