In the May edition of Diabetologia, researchers from Finland analyzed data from the Finnish Diabetes Prevention Study in the paper High-fibre, low-fat diet predicts long-term weight loss and decreased type 2 diabetes risk: the Finnish Diabetes Prevention Study. The conclusion in the abstract, "Dietary fat and fibre intake are significant predictors of sustained weight reduction and progression to type 2 diabetes in high-risk subjects, even after adjustment for other risk factors" is a text-book example of not letting inconvenient findings get in the way of your hypothesis.
Buried deep within the paper is the sentence, "The highest diabetes risk was seen among the high-fat/high-fibre and not, as would have been expected, among the high-fat/low-fibre consumers." Interesting, but not the focus of what I'd like to write about today.
Buried even deeper in the data are numbers that defy logic - of the 500 individuals participating in the study, 114 developed diabetes (22.8%) while on average they gained weight, experienced an increase in BMI and waist circumference while they reduced calories! That my friends is in stark contrast to the 386 who did not develop diabetes (77.2%), who also reduced calories but lost weight, reduced BMI and waist circumferance over the three year period.
Those who developed diabetes over the three years also had profound changes in their ability to metabolize glucose effectively - fasting glucose readings shot from 117ml/dL at the baseline to 128ml/dL after three years; and 2-hour glucose readings after an oral glucose challenge were worse too - up from 169ml/dL at baseline to 209ml/dL after three years.The researchers did not seek to investigate why these changes occured - how one gained fat while eating less calories as their glycemic control deteriorated over time.
Something interesting popped out in the discussion however when the reserachers included "In our study we emphasised adequate protein intake (0.8 g/1 kg body weight) but did not advise to increase it more than that. It is impossible to say whether advocating an increase in protein would have led to larger weight reduction than was achieved in our study. We did, however, also analyse the association of the protein intake (E%) quintile with weight reduction and diabetes incidence, but did not see any significant effects (data not shown)."
Why no data?
I did some calculating based on the macronutrients consumed in each group and something very interesting emerged - those who did not develop diabetes, were on average, consuming more protein than those who developed diabetes. In fact, they were consuming more protein even though they were consuming less calories!
It may seem like a very small difference, but the group that did not develop diabetes consumed 0.92g of protein/kg of body weight at baseline - and even with the calorie reduction, consumed 0.92g of protein/kg of body weight at the end of the study term!
Compare this to the group that developed diabetes - at baseline they consumed an average of 0.83g protein/kg of body weight, but by the end of the study had decreased protein intake at just 0.8g protein/kg of body weight.
So while the researchers stated they did an analysis of protein intake - they looked at percentage of energy and determined it wasn't significant and decided not to include the data.
If they'd taken the time to dig deeper - to see the protein intake by gram/kg-body-weight they might have come to a more interesting conclusion - dietary protein may in fact be correlated with development of diabetes in those with impaired fasting glucose when measured by intake in grams/kg-weight!
Those that did not develop diabetes had, just like those that did develop diabetes, impaired fasting glucose at baseline. Both groups reduced calories, both groups increased fiber intake, both groups lowered fat and carbohydrate intake as a percentage of energy and in real grams consumed - the difference in their macronutrient composition was their intake of protein. Those that did not develop diabetes maintained a constant 0.92g/kg-body-weight intake of protein; those that did develop diabetes reduced their intake of protein from 0.83g/kg to 0.80g/kg and gained weight on less calories!