Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults: Analyzing the study and data.
A recent study published in the prestigious Journal of American Medical association (JAMA), has concluded that “there was no significant difference in weight change between a healthy low-fat diet vs a healthy low-carbohydrate diet.” Interestingly, upon review of the entire publication, it is obvious that there is much more to the publication than what the authors decided to selectively comment on in the abstract.
1. “There was no significant difference in weight change…”
The key word here is “significant” or the implied statistically significant difference.The results of the study found that
“Weight change at 12 months was −5.3 kg for the low fat diet vs −6.0 kg for the Low carbohydrate diet.”
Clearly there is a difference between 5.3 and 6.0kg.
But, based on the way the authors decided to conduct their statistical analysis, they concluded that the difference is not significant.
Whether or not this difference is in fact negligible or not is debatable.
2. The low Carbohydrate group.
“The low carbohydrate” participants consumed 96.6g – 132.2g of carbohydrates per day.
According to the Institute of Medicine report Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids(IOM, 2002), the Recommended Dietary Allowance (RDA) for carbohydrates is 130 g per day. According to healthline, intake of 100g – 150g of carbohydrates would be considered “moderate” carbohydrate intake. To achieve a low carbohydrate-diet and associated metabolic effects, carbohydrate intake must be limited to 20-50g per day.
Therefore, the title of the paper and conclusions drawn are not fully accurate.
3. Other findings.
The participants in the study were also evaluated for parameters following the completion of the study.
It was found that the low-carbohydrate diet group:
– lost more % body fat
– had a larger decrease in waist circumference
– had a larger decrease in triglycerides
– had a much larger increase in HDL
– had a greater decrease in fasting glucose
– had a greater decrease in fasting insulin
The fact that all of these effects decrease the risk for cardiovascular disease is well documented in literature.
However, these findings were not reported in the abstract.
To conclude, a more accurate and all encompassing title for this paper would have been Low-Fat Vs. Moderate-Carbohydrate diet on 12 months weight loss and metabolic parameters in overweight adults. With this, the authors should have commented on the beneficial lipid marker parameters in the low-carbohydrate group.