Genetic differences in the effects of specific diets
Various health parameters were measured to observe how each diet affected the mice. They found that, overall, the Western diet had negative outcomes, including fatty liver disease and obesity. But, they also noted that the effects of each diet were significantly different, depending on the strain of mouse.
One strain, for instance, seemed to show no ill effects at all from the Western diet.
In another example, the Western and ketogenic diets, both high in fats, had polar opposite effects in two strains of mice. One strain showed negative outcomes from the Western diet, yet displayed no detrimental effects from the ketogenic diet. Another of the strains showed the reverse; they developed obesity and fatty liver disease on the ketogenic diet but were unaffected by the Western-style diet.
Across all strains of mice, the ketogenic diet caused the animals to burn off more calories without increasing their activity levels, but some mice ate so much that they still managed to become obese.
"We also found that the causes for obesity were different. Some mice on specific diets simply ate more calories, and this caused them to become obese. However, mice on other diets ate less but still became obese."
William Barrington, Ph.D.
Because mice respond in a similar way to nutrition and diet as humans, the researchers believe that there is a high chance that these results are relevant to people. Barrington says: "Since there are different optimal diets for different individuals, this underscores the need for precision nutrition, which would identify optimal dietary patterns for each person."
The findings have implications for anyone seeking to eat the healthiest diet for them. More broadly, they also bring into question recommendations from official bodies, such as the United States Food and Drug Administration (FDA). Their advice is based on average responses to specific diets and ignores individual differences.
The next step for the team is to try and pin down the genes responsible for the differences in reaction to dietary changes. In the future, they hope that their findings will lead to tests that will allow individuals to identify which type of diet is best for them.