A $170 million Nutrition for Precision Health program is underway, aiming to use artificial intelligence to determine the best diet for each person to prevent chronic disease. However, experts warn that short-term trials may not be sufficient to reveal the true effects of different diets on obesity and other health conditions.
The program involves several thousand volunteers on three different diets: a conventionally healthy diet, a highly processed diet, and a low-carbohydrate diet. While the investigators take great lengths to maintain scientific rigor, including providing fully prepared meals and monitoring participants’ intake, the trials are limited in duration – just two weeks each.
This short-term approach is inadequate for several reasons. Firstly, it may not be enough time to observe meaningful changes in weight or other health metrics. Secondly, factors such as utensil size, plate color, and social setting can influence eating habits, which can lead to biased results. Additionally, the use of a cross-over design, where participants consume all three diets in succession over several months, can also introduce carry-over effects that invalidate the trial.
In a hypothetical study comparing physical activity and sedentary behavior, exercise may be perceived as beneficial even after returning to a sedentary lifestyle, while being sedentary may be seen as less problematic than it really is. This phenomenon is known as a “carry-over effect” – a bias that can significantly impact trial results.
Furthermore, short-term diet trials are prone to “keto flu,” a condition where participants on very-low-carb diets experience fatigue and other symptoms due to their body adapting to the new nutrient intake. For volunteers with high intakes of carbohydrate, this bias works against low-carbohydrate diets.
Long-term studies, with diets and wash-out periods of at least two months, are essential to determine how specific diets support or hinder metabolism, inflammation, aging, and brain health. As seen in other areas of medical research, government funding plays a crucial role in supporting high-quality nutrition science, which is critical for developing evidence-based dietary guidelines and patient care recommendations.
The recent budget cuts highlight the need for every research dollar to count. Funding at the level of Nutrition for Precision Health could support several large-scale trials over two years, providing a solid foundation for future research and helping to combat diet-related chronic diseases.
Source: https://www.statnews.com/2025/04/22/nutrition-precision-health-short-term-diet-trials-chronic-disease-food