The Effects of Diet on Life Expectancy
It is somewhat interesting to see a careful analysis of diet and life expectancy, using the sizable UK Biobank population, that does not contain any of the words "calorie", "weight", or "obesity". The effects of calorie intake on health over the long-term are sizable, even if we focus only on mechanisms associated with the gain of weight. Visceral fat is metabolically active, generates an increased burden of senescent cells, and contributes to the chronic inflammation of aging via a range of different mechanisms.
Thus one would assume that buried underneath this set of data on what it is that people eat is a more relevant and useful set of data that incorporates both dietary components and calorie intake, and which is only mentioned in passing in this paper. Certainly, it is the case that people who eat more processed and less healthy foods are usually consuming significantly more calories than the few who put in an effort to garden their diet, and are usually going to carry a greater burden of visceral fat.
In this paper, we present a method for estimating changes in life expectancy following changes in food choices, considering correlation between mortality and food group intakes, and effect delay. Such estimates may be useful particularly for policy purposes and for underpinning both guidance and interventions for improving public health. Our results indicate that UK adults aged 40 years with median dietary patterns can expect to gain approximately 3 years in life expectancy from sustained changes to the longevity-associated dietary patterns. Importantly, the estimated gain in life expectancy is approximately a decade for those shifting from the unhealthiest to the longevity-associated dietary patterns. Overall, the bigger the changes made towards healthier dietary patterns, the larger the expected gains in life expectancy are.
Consuming less sugar-sweetened beverages and processed meats and eating more whole grains and nuts were estimated to result in the biggest improvements in life expectancy. Sensitivity analysis also adjusting for body mass index and energy consumption indicated that body mass index and energy consumption might partially mediate and/or confound a possible beneficial effect between life expectancy and whole grains, vegetables and fruits, and inversely for red meat and eggs. For white meat, associations were stronger when adjusting for energy intake and body mass index, while the situation was mixed for legumes. These estimates correspond well with meta-analyses on associations between intakes of food groups and mortality.
Unsurprisingly, predicted gains in life expectancy are lower when the dietary change is initiated at older ages, but these remain substantial. For example, we estimated that people at the age of 70 years could expect to benefit from about half of the life expectancy gain predicted for adults at the age of 40 years, equivalent to a gain in 1.5 years when optimizing median dietary patterns and 4-5 years for those shifting from the unhealthiest dietary patterns. The UK population currently has a life expectancy at birth of 83.6 years for females and 79.9 years for males, and a 3 year gain in life expectancy associated with changes from median to longevity-optimized dietary patterns from the age of 40 years. Life expectancies have steadily increased over time, and the observed increase is parallel to the changes in life expectancy observed in the United Kingdom over the past 15 years. A large shift towards healthy dietary patterns could contribute substantially to meeting the Sustainable Development Goal target 3.4 that aims to cut premature mortality by one-third.