For decades, we've been pursuing
a low-fat diet as a public
health message. Then all of a sudden there seemed to be
a flip-flop. People said the low-fat thing was wrong.
It was the opposite, it was supposed to be
low-carb. It seems like there's
been this very active debate and opponents on either side. The
acronym for our study is the
DIET FIT study. We don't really
think there's one diet for
everyone. One of the issues that
would help people, if we could
find out which diet is best for
whom. In this particular study,
we wanted them to both be very
high-quality low-carb and very
high-quality low-fat. We wanted
them to be huge differences. We
actually weren't sure how far we
should push people. We came up
with this idea that we would
push both groups in the first
eight weeks of the 12-month
study to try to get to 20 grams
of fat or 20 grams of carb. If
you don't know much about diet,
those are huge changes from what
they had at baseline. Another
point we hit home all the time
was quality. Want you to go to the farmers' markets, want you
to cook more for yourself, want
you to sit down with your family.
Don't want you to snack in front
of the TV, don't want you to eat
in the car. We told both groups,
low-fat and low-carb, as little
or no added sugar if possible,
as little or no refined grain if
possible, and as many vegetables
as you can. With that as the
backbone, they went in their low-
fat or low-carb direction. This
required quite a few people. We
ended up with 609 enrolling in
the study with more than 300
assigned to each diet. All of
them were this wide range of
genetic predisposition
potentially, and insulin/glucose
regulation variability
potentially. The premise was
that if we teased that apart and
then looked by diet group,
could we explain the individual
variability that we consistently
see in these studies? That's
what we were after. In order to
test the hypotheses we had going
into this study, we had to meet
a lot of the assumptions that we
thought we would get. One of
them was that people would lose
a lot of weight in a weight-loss
study. They did. They lost
collectively 6,500 pounds. The
other thing that had to happen
was that we needed people to
have a wide variability of
weight change on both diets.
Some of the participants lost 40,
50, 60 pounds, some gained 10 to
20, and everything in between.
At the end of the day, neither
of our original hypotheses
proved to be true. There's a low-
fat genotype. There was a low-
carb genotype. High percentages
of people fell into both
categories, not predictive at
all of who was more or less
successful on either diet. No
matter what their insulin
glucose dynamics were, in our
hands, there was no ability to
predict if one diet was better
than another. Close the doors
on our original two hypotheses,
but the future is full of
opportunity for building on this
study. People are going to want
to know what to recommend. Not
going to recommend low-fat over
low-carb, or vice versa, because
that's not what we found.
Depending on how you choose to
define low-fat or low-carb in
terms of food choices and food patterns, you can make a
plausible mechanistic link
between either camp, low-fat or
low-carb, and better health. The
more I've looked into this, the
more conferences I go to, I
continually see three factors
come up again and again. Get rid
of added sugar, get rid of
refined grain, and eat as many
vegetables as you can. Those
are all enormous challenges in
the American diet and many diets
globally. Yet, we're battling
about points on the fringe of
this whole debate without
getting to the core. I think if
we really focused on added sugar
and refined grain decrease or
elimination, and we worked with
some of our favorite chefs to
make vegetables even more
unapologetically delicious, a
lot of the debates would go away...