They contribute, but on their own they're not likely to add decades to lifespan or otherwise drastically reduce the risk of age-related disease and disability.

They contribute, but on their own they're not likely to add decades to lifespan or otherwise drastically reduce the risk of age-related disease and disability. An effect is clearly there, but it's just not big enough to explain the range of results seen. Much of this is likely to be a complex of gene/lifestyle interactions. It's known that some people metabolize saturated fat differently because of genetic variations, for example [1]. Likewise, there is a great deal of variation in physiological responses to exercise, for which genetic variation is a prime suspect [2]. To understand how dicey a lot of recommendations are, be sure to look not just at the average outcomes in the studies, but also the range and distribution. Abstracts and news articles often obscure a situation in which some get worse, some have no significant change, and some respond unusually well. Others spin the situation to say that everyone benefits from an intervention... as long as you include enough outcome measures that at least one of them improves for each subject and ignore all the outcomes that get worse [3]. [1] https://en.wikipedia.org/wiki/Apolipoprotein_E https://en.wikipedia.org/wiki/Apolipoprotein_E [2] https://www.ncbi.nlm.nih.gov/pubmed/26767377 https://www.ncbi.nlm.nih.gov/pubmed/26767377 [3] https://www.ncbi.nlm.nih.gov/pubmed/25717010 https://www.ncbi.nlm.nih.gov/pubmed/25717010