A team led by Dr. David Ludwig from Boston Children’s Hospital that reviewed diet trials found that 86% of such studies “lacked rigor” and were prone to bias. Ludwig adds that diet research is also severely underfunded.

Nathan Gray filed this report in NUTRA:

When the teams compared the original ClinicalTrials.gov registry descriptions with the final published papers they found that 18 diet trials (86%) showed ‘substantive discrepancies’, while only two of the drug trials (22%) had similar levels of discrepancy.

According to the authors, these changes typically involved a change in the time frame of the primary outcome or the number of co-primary outcomes. One diet trial, for example, initially listed ‘weight at five years’ as the primary outcome, but later amended this to ‘change in body fat at one year.’

Other trials initially planned several primary outcomes or measurements at several time points, but later pared these down to a single outcome or single time point in the published study.

The team noted that problems with diet trial registries may arise due to their greater heterogeneity and lower budgets when compared to drug studies “and the inadequacy of infrastructural support for nutrition research.”

Ludwig and colleagues also suggest several immediate remedies, such as creating specialised registries for diet trials to reflect their special challenges, but also called for ‘a sort of Manhattan Project’ to pin down the effects of diet changes once and for all.

They note that while this would require a substantial investment, “the amounts involved would total a fraction of a cent for every dollar spent treating diet-related conditions like obesity, Type 2 diabetes, and cardiovascular disease.”y and psychological well-being across extended periods of Healthy Longevity.