{For
personal reasons, mainly involving the restoration of an 1843 cottage in Dublin’s
south coastal village of Blackrock, I have been absent from blogging for a
while. I’m back now with renewed vigour to pursue the best of nutrition science
and to tackle, mercilessly, nutribabble.}
One of
the latest trends in nutrition is to reduce our focus on nutrients and to
sharpen our focus on the role of particular food patterns in promoting health.
High up on the list of foods to avoid are processed (or ultra-processed) foods or foods high in fats,
refined sugars and salt. A recent paper from Stanford University has been
widely cited (not by the authors) as evidence that advice on caloric intake is less important in weight loss than the
quality of the diet consumed[1]. In
this study which was well designed, with adequate statistical power and ample
duration, the authors describe the advice given to subjects (all were obese) thus:
“No explicit instructions for energy
(kilocalories) restriction were given. Both diet groups were instructed to (1)
maximize vegetable intake; (2) minimize intake of added sugars, refined flours,
and trans fats; and (3) focus on whole foods that were minimally processed,
nutrient dense, and prepared at home whenever possible.” There were two
treatment groups: a high-carbohydrate, low-fat diet and the opposite, a high-fat,
low-carbohydrate diet. The two groups were given dietary advice to achieve the
food pattern outlined above. Both groups lost weight after the 12 moths of
intervention to the level of about 5.5 ( lbs) on average.
Here is how the New York Times reported the
findings (Anahad O’Connor February 8th, 2018): “Anyone
who has ever been on a diet knows that the standard prescription for weight
loss is to reduce the amount of calories you consume. But a new study,
published … in JAMA, may turn that advice on its head. It found that people who
cut back on added sugar, refined grains and highly processed foods while
concentrating on eating plenty of vegetables and whole foods — without worrying
about counting calories or limiting portion sizes — lost significant amounts of
weight over the course of a year”. A distinguished Dean from Tufts in Boston was quoted as saying: “The research lends strong support to the
notion that diet quality, not quantity, is what helps people lose and manage
their weight most easily in the long run. It also suggests that health
authorities should shift away from telling the public to obsess over calories
and instead encourage Americans to avoid processed foods that are made with
refined starches and added sugar, like bagels, white bread, refined flour and
sugary snacks and beverages”. The
NYT piece was quoted across the globe by lazy editors to fill column inches
with a pretty impressive story. Regrettably, it was a misleading story which
opted to hide from its readers one awfully important point.
You see, the JAMA paper gives data on caloric
intake at the beginning of the study and also at 3, 6 and 12 months of the
intervention. Right throughout the study, irrespective of which of the two
diets were being followed, no differences were seen between the two groups in
calorie intake. So, for convenience of communication, I’ll give the average values
of the two treatments at the different times. At baseline, the average daily
caloric intake was 2150. By month 3, it had fallen to 1580. It then rose to
1620 by month 6 and at the 12 month conclusion, it was 1700. Thus, the 12 month
figure was all of 450 fewer calories consumed
every day. The average body mass
index (BMI; kg/m2) was 33, which means that the two groups were well
into the obesity category of body weight. At that body weight and that daily
caloric deficit from food alone, weight loss was no miraculous discovery. Which
raises now a few questions.
Why were readers of the New York Times (NYT)
misled so as to believe that calories don’t matter in weight loss? Is it so
obvious to the NYT that the food patterns recommended were somehow so bound to
lead to a caloric deficit that it needn’t be mentioned to its readers? Or is it
remotely possible that the NYT never really read the paper and thus missed this
whopping caloric deficit? I doubt I’ll ever know the answer. But if I was a
journalist, I would be inclined to poke a bit further into this paper. We know
from the paper that there was considerable variability in weight loss but no
data are given. We also are not given any data about the changes that occurred in
food intake , particularly to provide supporting data on the target foods (less
of the sugary type, more of the complex carbohydrate food, more vegetables etc.).
But the big question is why was the average relapse so low? Thus at three
months, the mean daily caloric intake was 1580 and by month 12, it had slipped
back a bit but only to 1700 kcal per day, a 9-month average regain of just 120 kcal
per day. The human body absolutely defends a prevailing weight such that as all
dieters know, the maintenance of weight loss requires enormous perseverance.
Take your eye off the tiller for one moment and the tidal wave of our
obesogenic environment will sweep you back on the rocks. So why not on this
diet? I don’t know the answer to that but I do know that the anti-processed
food lobby will argue that it is proof that processed food fosters a false
appetite and that once that is taken away with a change to minimally processed home
prepared foods, appetite regulation returns and low energy intakes are the
result. There is however a little fly in the ointment here from another paper
which set out to study the link between the intake of ‘ultra-processed foods’
and cancer[2].
This study from France used a cohort recruited
through the Internet and who had their diet analysed through digital
interaction using a multiple pass 24-hour recall. In all, 104,980 subjects were
eligible to participate and did so over the period 2009-1017. The study was about cancer and that
will not feature in this blog. Rather, we will focus on the weight of these
subjects expressed as BMI (kg/m2).
The population was divided into quartiles according to the contribution (weight
by weight) of ultra-processed foods to overall food intake. The respective
contributions (% w/w) of ultra- processed foods to the diets of the French
subjects were thus: Q1 = 9; Q2 = 14 ; Q3 = 20 and Q4 = 32. And across this
spectrum of ultra-processed food intake, BMI remained constant to the first
decimal point at 23.8 kg/m2. The literature abounds in studies
linking ultra-processed foods to obesity. Mais apparemment, pas en France. (But
apparently, not in France).
So returning to the Stanford study, we have no
differences in weight loss between those on a low fat-high carbohydrate diet as
opposed those on a high fat-low carbohydrate diet over a 12 month period. They
showed precisely the same caloric deficit over that period so one concludes
that it simply doesn’t matter what advice one is given for a reduction in fat
or in carbohydrate, the bottom line is that if that advice leads to a calorie
deficit, then weight loss will accrue, irrespective of what the NYT might say.
Quite how there was so little mean relapse in this study is as yet unexplained
but as mentioned above, the anti-processed food advocates will argue that the abandonment
of such foods returns people to a diet where appetite control in returns. The
fly in the ointment of the French paper will never be raised.
Fine up to a point. However, a previous NIH funded study, the “Pounds Lost
Study” with weight loss programmes varying in fat and carbohydrate and reaching
a similar conclusion to the Stanford study, showed a steady weight loss to 12
months with a significant weight loss relapse thereafter[3].
My calculation of the data presented in the tables of the Stanford study is
that the average resting metabolic rate might be about 1,450 kcal per day which
might not seem a million miles from the reported energy intake at 12 months, 1,700
kcal. However, the former is calculated based on weight stability but with
dieting, this will fall by about 15%[4] to
1,230 kcal/d. Either these people will continue to lose weight or that deficit
will drive a weight regain process. All the available science would show a slow
relenting return to original bodyweight in a large proportion of the
population. Maybe the Stanford study will show that better investment in food
choice and tutoring on home cooking might help. Here’s hoping it does.
This Stanford study is very well designed, well
executed and fairly reported. More data on food intake (% consumers and
consumer only intake) would have been welcome but there’s only so much one can
do for modern journals with page restrictions and charges. It adds
significantly to the data on the relative role of the main energy macronutrients
(carbohydrate & fat) and it is consistency with existing data. Regrettably,
it will be long cited out of context as the study which showed that its diet
quality that counts, not calories.
[1] Christopher D. Gardner, PhD; John F. Trepanowski, PhD;
Liana C. Del Gobbo, PhD; Michelle E. Hauser, MD;
Joseph
Rigdon, PhD; John P. A. Ioannidis, MD, DSc; Manisha Desai, PhD; Abby C. King,
PhD . Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in
Overweight Adults and the Association With Genotype Pattern or Insulin
Secretion The DIETFITS Randomized
Clinical Trial. JAMA. 2018;319(7):667-679. doi:10.1001/jama.2018.0245
Méjean,Mélanie
Deschasaux, Philippine Fassier, Paule Latino-Martel,
Marie Beslay, Serge Hercberg,, Céline Lavalette, Carlos A Monteiro,
Chantal Julia, Mathilde Touvier; Consumption of ultra-processed foods and
cancer risk: results from NutriNet-Santé prospective cohort; BMJ 2018;360:k322
| doi: 10.1136/bmj.k322
[3] Frank M. Sacks, M.D., George A. Bray, M.D., Vincent J.
Carey, Ph.D., Steven R. Smith, M.D., Donna H. Ryan, M.D., Stephen D. Anton,
Ph.D., Katherine McManus, M.S., R.D., Catherine M. Champagne, Ph.D., Louise M.
Bishop, M.S., R.D., Nancy Laranjo, B.A., Meryl S. Leboff, M.D., Jennifer C.
Rood, Ph.D., Lilian de Jonge, Ph.D., Frank L. Greenway, M.D., Catherine M.
Loria, Ph.D., Eva Obarzanek, Ph.D., and Donald A. Williamson, Ph.D.
Comparison
of Weight-Loss Diets with Different Compositions of Fat, Protein, and
Carbohydrates; N Engl J Med 2009;360:859-73
[4] Erin Fothergill, Juen Guo, Lilian Howard, Jennifer C.
Kerns, Nicolas D. Knuth, Robert Brychta, Kong Y. Chen, Monica C. Skarulis, Mary
Walter, Peter J. Walter, Kevin D. Hal; Persistent
metabolic adaptation 6 years after “The Biggest Loser” competition; Obesity (2016)
24, 1612-1619. doi:10.1002/oby.21538
