Another study that shows one way of dieting is better than another suffers from the same problems as all of them.
Low Carb Is Better (Again)
Low carb fans currently freak out over this study, that shows how superior their lifestyle is for reducing weight compared to a low fat diet.
Really? Or will this be another exercise in counting your carbs before not trimming the fat off the sirloin steak?
The latter, because a trivial calculation makes the low carb superiority disappear into a cloud of saturated bad math sizzle.
Caloric Math For Beginners
To get my drift on this read the full study or, if you don’t have access to Annals, head over to MedPage Today, whose author cites the relevant numbers.
Got it? Ok. The self-reported daily calories showed the low fat group on average ate 79 kcal more per day. 79 x 365 = 28,835 kcal. Losing 1 lb of weight requires a deficit of ~3,500 kcal, which means 28,835 / 3,500 = ~ 8 lbs or 3.6 kg. According to the study, the low carb group lost 5.3 kg, the low fat group 1.8 kg.
What do you get when you add 3.6 + 1.8? 5.4 kg.
28,835 Calories? Ah, Those Aren’t Significant!
I asked Dr. Lydia Bazzano, the study’s lead author, about the discrepancy in calories between the low carb and fat groups. She replied:
The differences are not statistically significant except at 3 months so it’s not possible to say that these differences are not due to random chance variation at 6 and 12 months. So no, in my opinion it does not explain the difference. But a better question is why would there be a difference at 3 months? Fat and protein provide a feeling of satiety or fullness and perhaps that led them to eat less? Another issue is the loss of more fat as a proportion of the weight lost in each group in the LC group. Calories in/calories out doesnt explain that.
Yeah, the difference may not have been significant most of the time, but a total difference of 28,835 kcal is.
Unless, of course, you follow Dr. Bazzano’s line of reasoning that a calorie is not a calorie. It’s a mindset low carb aficionados readily embrace, but I’m surprised that a qualified scientist resorts to it for an explanation.
Going With The Times
In my opinion it was a badly set up trial that provided the low carb superiority and not any inherent advantage of eating low carb.
But when I read about this in the New York Times their author couldn’t hide how amazed he was:
[…] More recent clinical studies in which individuals and their diets were assessed over time have produced a more complex picture. Some have provided strong evidence that people can sharply reduce their heart disease risk by eating fewer carbohydrates and more dietary fat, with the exception of trans fats. The new findings suggest that this strategy more effectively reduces body fat and also lowers overall weight.
This makes me grind my teeth. Before publishing statements this strong, one would think that a New York Times reporter closely scrutinizes the study he writes about. The math doesn’t require a science degree and if I was able to inquire with Dr. Bazzano, a New York Times reporter noticing this discrepancy should be too.
Calories In Vs. Out
Who’d have thought?
Picture courtesy of Steve Snodgrass.