[…] Because the ultimate goal is to identify the environmental triggers of obesity, experiments should, ideally, be directed at elucidating the processes that lead to the accumulation of excess fat. But obesity can take decades to develop, so any month-to-month fat gains may be too small to detect. Thus, the first step that NuSI-funded researchers will take is to test the competing hypotheses on weight loss, which can happen relatively quickly. These first results will then help determine what future experiments are needed to further clarify the mechanisms at work and which of these hypotheses is correct.
He then describes the composition of this experiment: In the first stage, 16 subjects (obese and overweight) will be housed in a research facility and cycled through three diets. The first will mimic the average American diet (50% carbs (of which 15% will be sugar), 35% fat and 15% protein). Using a metabolic chamber to assess energy expenditure, calories will be adjusted up and down until the subjects are maintaining a steady weight.
In the second stage, these same subjects will be switched to a low carb diet consisting of about 5% carbohydrate, 15% protein and 80% fat. These subjects will consume the same number of calories as in Stage 1, spread out across an identical feeding schedule.
So what is this going to test? Taubes lays it out:
…if fat accumulation is primarily driven by an energy imbalance, these subjects should neither lose nor gain weight because they will be eating precisely as many calories as they are expending. Such a result would support the conventional wisdom—that a calorie is a calorie whether it comes from fat, carbohydrate or protein. If, on the other hand, the macronutrient composition affects fat accumulation, then these subjects should lose both weight and fat on the carbohydrate-restricted regime and their energy expenditure should increase, supporting the idea that a calorie of carbohydrate is more fattening than one from protein or fat, presumably because of the effect on insulin.
I think the world has waited long enough for this experiment. Let’s wish NuSi luck. Whatever the results show, we’ll all hopefully have a much more informed understanding of obesity, weight loss and weight gain.
- , Gary Taubes. Scientific American, September 11, 2013.
- Good Calories, Bad Calories, Gary Taubes.
- Why We Get Fat, Gary Taubes
- Nutrition Science Initiative (NuSi). (Website)