Could your healthy diet make me fat? An Israeli study at Weizmann Institute of Science in 2015 about personalized nutrition was heralded by a media frenzy. “This diet study upends everything we thought we knew about ‘healthy’ food,” claimed one headline. The study suggested that dieters may be mistakenly eating a lot of some foods, like tomatoes, that are good for most people, but bad for them. And it raised the possibility that an individualized approach to nutrition could eventually supplant national guidelines meant for the entire public.
Personalized medicine has already become well established in clinical practice. We know that the effects of some drugs vary from person to person and that genetic analysis of tumors can help doctors select the best cancer treatment for a particular patient. Despite the recent fanfare, we have also known for a long time that people respond differently to specific foods based on their genes, past health or other factors.
Standard diets typically fail to produce significant long-term weight loss. For instance, while a clinical trial published in 2005 of 160 adults randomly assigned to the Atkins, Ornish, Weight Watchers and Zone diets reported modest results in all groups after one year, individuals in those groups experienced weight changes ranging from a loss of 35 pounds or more to a gain of 10 or more.
This variation is commonly attributed to behavior. Some people are simply more motivated and compliant with their assigned diet than others. But suppose the people who did poorly on the low-fat Ornish diet would have done well on the low-carbohydrate Atkins diet because of their biological makeup, and vice versa? If we knew that ahead of time, we could assign everyone the diet that’s best suited for him or her.
Despite the hype, personalized nutrition is not ready for practical application in the clinic. But this exciting field of research may help explain why people respond so differently to diet based on biology. In this way, personalized nutrition may build upon, rather than substitute for, national dietary guidelines, providing a common ground for all sides in the “diet war” to declare a truce.