Thursday, March 8, 2012

What weight loss?
You have probably heard one or the other diet guru claiming that manipulating the nutrient composition of your diet will make you lose weight. Well, for those of you, who stubbornly cling to the notion that excess weight is simply a matter of too many calories-in vs. too few calories-out, here is the good news: You are right, after all. It really doesn't matter.

In an exemplary 2-year study New Zealand researchers compared the effectiveness of a low-fat high-protein diet with an equally low-fat but high-carb diet Not only was there no difference at all between the diet groups into which the participants had been randomized. Their mean weight loss was a paltry 4 Kilos. Nothing to scream about when you look at the mean starting BMI of 36 and a mean body weight north of 100 Kilos.

The primary outcome parameters, that is blood sugar and HbA1c, which is what you are really after, when you try to lose weight as an overweight diabetic, didn't improve a bit. Well, there was some improvement after 6 months, but by 24 months the participants were back to square 1. Does that sound familiar?

Now, let's not get ahead of ourselves and let's look at what makes this study exemplary. First the researchers took in 419 overweight, diabetic participants for 24 months (which is really a large number and a long duration relative to what is typically the case for such dietary intervention studies). These participants were randomized into one of the two dietary groups. Each participant received individualized dietary advice on how to achieve a daily 500 kcal energy deficit. In the first year each participant was given 18 dietician-led group meetings with no more than 12 people per group. Follow-up measurements of body weight, waist circumference, diet composition and a host of biomarkers were done at baseline and at 6, 12 and 24 months. And then what happened?

30 Percent of participants dropped out right away in the first year. While HbA1c and blood glucose had dropped slightly but with statistical significance in the first 6 months, these markers remained deep in the red danger zone with > 7.7% and 7.9 mmol for HbA1c and glucose respectively. Which emphasizes the point I always like to make: there is a difference between statistical significance and clinical relevance. The latter wasn't there at 6 months and certainly not at 24 months when both had come back to their baseline levels. All the other biomarkers, which you probably know from your personal risk profile, such as cholesterol, triglycerides and blood pressure, didn't show any improvement at all. Neither was there a difference between the diet groups.

So, are we, and the researchers, right to claim that it is only calories which count, and not the macronutrients which deliver them? In my view, the study doesn't really answer the question. The weight loss was possibly too small to detect any difference. From personal experience (as a diet guinea pig and as one who does research with overweight people), replacing carbs with protein does have an effect on body weight. But comparing the typical energy density of a lean piece of meat with that of, say, bread, the differential weight effect might well come from the fewer calories the meat delivers in a meal of equal weight. Which would, again, make it an issue of calories, not of macronutrients. I also have some misgivings about randomizing diabetics into any high-carb diet.

My personal reading of this study? Well, I admit I'm biased against any weight loss attempt that is purely based on diet without physical activity as a component to achieve a calorie deficit. I'm also biased against calorie counting, which really is only for masochists and for those who mistakenly believe that they can estimate their calories reliably. But more on that another day. Which is why in our health science lab we have developed that tool for people to train a 6th sense for calorie balance. It really is the simplest way of getting your weight where you want it to be in an intuitive, playful and amazingly low-effort way. Try it out here: Maybe you won't fall for those gurus any more. And maybe, just maybe, you'll know how to deal with the calorie cartel.


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