HORSE SENSE FOR WEIGHT LOSS
David
L. Katz, MD, discusses the implications of the JAMA study that compared
low-fat and low-carbohydrate diets for weight loss and health
improvement and also profiled the genes of the participants to determine
if the genetic patterns thought to predict success on a given diet
actually did so. The following edited extract is reproduced with his
permission.
“The study, run by Professor
Christopher Gardner at Stanford University, randomized over 600 adults
to either a fat-restricted or carbohydrate-restricted diet making both
diets as ‘good’ as possible. The result was that significant weight
loss, and health improvement measured in all the usual ways, occurred in
both treatment assignments. Going from the generally poor baseline diet
that prevails in America to either a healthy, low-fat diet that
emphasized vegetables, and whole, minimally processed foods; or to a
healthy low-carbohydrate diet that also emphasized vegetables, and whole
minimally processed foods produced significant, and very comparable
benefits.
Study participants were not told to track or
reduce calories, but by shifting to a much higher-quality diet, they did
so as a by-product. Both groups cut their daily calorie intake by about
500 to 600 kcal daily (2100–2510 kilojoules), and lost the amount of
weight that would portend. They achieved this by eating wholesome foods
in sensible combinations, and by applying some rules and discipline to
diets that had neither at the start.
Genetic markers of
expected success on one type of diet versus the other proved to be of
no value. Weight loss in each diet arm was indistinguishable between
those with a genetic profile saying they should do especially well, and
those with profiles suggesting they should struggle. Nutrigenomically
customized weight loss, despite the buzz it generates, is clearly not
ready for prime time.
The study also found no
relationship between baseline insulin status and success on a given diet
assignment. The high-profile claims that weight loss is all about
reducing carbs to reduce insulin prove to be apocryphal. A shift to
wholesome foods in sensible combinations is effective at lowering weight
and improving health regardless of fat or carbohydrate levels, even
among those with insulin resistance at the start.
Fundamentally,
then, this study suggests that the best way to lose weight and improve
health with diet is not by fixating on macronutrients or calories, but
by eating wholesome foods in some sensible combination, and emphasizing
whole, minimally processed plant foods. The study also indicates that
the fundamentals of generally healthful eating pertain to us all,
regardless of our genes or insulin levels.
These
findings of science may surprise some, but they don’t much surprise me,
and the reason is – sense. Horse sense, in particular. With horses, as
with every species other than our own, we tend to think about the kind
of diet that is generally right for the kind of animal, rather than the
need to customize diet to each individual. Of course, the one does not
preclude the other; horses can all be fed like horses, but some horses
will need extra grain to maintain their weight, some will do better on
certain varieties of hay. But from the start, the focus is on the common
theme of a healthful diet for an entire species, and only after that,
variations on the theme.
The DIETFITS study findings
collectively indicate that the fundamentals of a health-promoting
dietary pattern for Homo sapiens matter more than customizing on the
basis of inter-individual variations. As with horses, the one does not
preclude the other – but the science we own at present better empowers
us to customize diet based on preference, rather than genes. It is good
to know that when it comes to dietary patterns that are best for health,
we do have choices among the variants on a common theme.
Dr.
Katz proudly notes that DIETFITS Principal Investigator, Prof. Gardner,
is a science advisor to his company, DQPN, LLC, devoted to reinventing
dietary intake assessment for the digital age.
About David L. Katz
• Director, Yale University Prevention Research Center; Griffin Hospital
• Immediate Past-President, American College of Lifestyle Medicine
• Senior Medical Advisor, Verywell.com
• Founder, The True Health Initiative
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