>From Enrico:
>>Nevertheless, there were "low fat dieters" who even ate more fat and
"non dieters" who, for some reasons, actually ate less fat, just as
some "dieters"... <<
Yes, this was a very real world study. 50,000 women followed over 7
years. Unless you put people in jail, you can't control what they'll
eat. I wouldn't be at all surprised were there so called "low fat"
dieters who tried the Atkins Diet at some time or other.
>>Mostly low fat dieters, I suppose, both in the intervention and
control groups, right? <<
Well, I'm sure that there were off an on dieters on many different
types of diets in both groups over the seven years of the study. At
the study's conclusion, though, the so-called "low fat" group was
eating 30% calories as fat (down from 38.8% pre-study) and the control
group was eating 38.1% calories as fat (down from 38.8% pre-study), so
it appears that few in either group were following what I'd call a low
fat diet (and certainly nowhere near the 20% target for the low fat
group). But, again, this is real world. You can lead a turkey to water
but you can't make him gobble.
>>Seven years is a long time. When were the variations in dietary fat
and weight measured? <<
Women in both groups were contacted by telephone every 6 months for 7
years and had annual physical exams, where height, weight, waist, and
hip circumference were measured. Physical activity and dietary intake
were regularly monitored for all subjects during the 7 years of the
study. (from the "Methods").
Quoting me:
> Note the perfectly linear relation between percent changes in percent
> calories as fat and weight change, REGARDLESS of which group the
> subjects were in. Those subjects who reduced fat intake
Enrico says:
>>Id est the dieters who actually dieted, in the "low fat diet"
intervention group...
>>Even in the control group, though, fat reduction might be due to some
sort of personal dieting... We are talking of obese women and low fat
dieting is quite common, isn't it? <<
All types of dieting is common in obese women.
Enrico:
>>About 1 kg average weight loss (in the control group) after 7 years is
not exactly a huge success for obese women, is it? All in all, they
were still obese. <<
It was NOT a weight loss intervention study. That was never the
purpose of the study. What was important about the study was not the
"success" (or lack thereof) of the intervention, but rather the quality
of the data collected. Compliance in the intervention group wasn't all
that great and there was no exercise program (without which all long
term weight loss programs are constrained to fail in the vast majority
of participants). So some "control" subjects cut their fat intake on
their own, and some intervention subjects actually increased their fat
intake from baseline. What's important, though, is the striking,
perfectly linear inverse relationship between fat intake and weight
change.
>>Only 0.5 kg average weight gain after 7 years binging on fat?
Not bad, for non-dieters with no exercise!
(I suppose they were non-dieters as low-fat dieters who actually
dieted... reduced their dietary fat as a result, of course, thus
should not be found in that quintile). <<
This isn't "binging" on fat. The average intake of all study
participants at the start of the study was 38.8%. That's significantly
more than is the case for the average person in the US at the time of
the study. All the women were obese at the start (average BMI 30). On
average, those who didn't change their baseline fat intake didn't
change their weight. Those that increased it gained weight. Those
that decreased it lost weight. The changes in weight were directly but
inversely proportional to changes in fat intake.
The absolute magnitude of changes in a very heterogeneous population
underestimate the importance of the differences in the changes being
measured. If all forms of cancer were cured today, then average life
expectancy would be improved by only about 2 years.
>>Would you call 24% fat a "fat restricted diet"? I'd regard that as a
quite balanced diet instead, neither high nor low in fat. <<
Well, the average percent fat intake for Americans is on the order of
34%. So 24% represents a 30% reduction, compared to average. But we
can infer (from the study in question, for example) that obese people
may have even higher fat intakes (the 50,000 obese women in this study
ate an average of 38.8% fat, pre-intervention; so compare 24% with
38.8% and that's quite a reduction. Also, please note that many
so-called "low fat" diet studies have used 30% calories as fat as the
definition of a so-called "low fat" diet!
>>I would like to know if those who reduced dietary fat and lost weight
ate less calories as well. I strongly suspect that that is the case,
because of two reasons:
1) low-fat diet was the suggested weight control diet and is a common
pattern for personal diets as well,
2) it's easier to change quantities in dietary fat than in carbs or
protein. No one eats, say, just fat and no carbs or protein. On the
other hand, it's possible to eat protein and carbs and (almost) zero
fat... <<
Well, of course they ate less calories. Unless you increase exercise
(and there is no evidence that the "low fat" group increased exercise)
the only way you can lose weight is to reduce calories. This confirms
many studies which show, in an ad libitum situation, that reducing fat
content of ingested food leads to lower ingestion of calories.
At the beginning of the study, average caloric intake was 1788 calories
for intervention group and 1789 for control group. After 7 years,
average caloric intake was 1446 for the intervention group and 1564 for
the control group.
>>I rather promote calories, lack of exercise and
non-satiating/palatable foods as a possible cause of obesity. <<
I mostly agree. I'd put lack of exercise number one and slight
increases in total caloric consumption as number two.
>>I agree with Jim Chinnis's remarks...
In other words, it seems that the graph applies within the context of
a high-carbohydrate diet, but doesn't tell much about low carbers. <<
When you guys refer to "low carbers," I presume that you mean extreme
(e.g. Atkins style) low carbers? This was in no way a specific study
of the Atkins diet. The results pertain to Americans eating pretty
much standard American diets (I gave the 95% confidence intervals for
intake of carbs and fats in other message).
- Larry W
