In a previous article we discussed the principles behind caloric restriction as a means towards increasing lifespan and improving the healthspan (time to occurrence of aging-related disease). However, since caloric restriction is a quite dramatic intervention involving between a 20-40% reduction in the caloric intake and therefore, among other issues, hard to maintain in the long term, here we present other alternative dietary interventions pursuing the same aim: to delay the aging process and promote a longer lifespan.
Among the new alternatives to a sustained caloric restriction stand time-restricted approaches such as short-term starvation, periodic fasting, fasting-mimetic diets and intermittent fasting. Fasting, mostly known to the mayority of us as a caloric deprivation performed for religious reasons, in our specific context, refers to either a complete food deprivation or 60% or higher caloric restriction. Whereas in the case of religious fasting, this state is maintained over a period of days to weeks (Ramadan), intermittent fasting would be performed every other day, while periodic fasting would be repeated periodically (every two weeks, month, etc.) for two or more days at a time. Both periodic and intermittent fasting have been shown to increase lifespan and to have effects on similar metabolic pathways as caloric restriction, even when the overall caloric intake is not reduced with fasting. A fasting mimicking diet, comprises a low calorie, low protein diet which resembles fasting in its physiological response, and has been shown to enhance the healthspan, among other positive effects.
Since cutting down on eating might not be so desirable for some, another alternative has been recently posed to improve healthy aging: normo-caloric diets with planned deficiencies (in particular macronutrients: proteins, carbohydrates, etc.). The most effective macronutrient restriction so far is reducing protein and/or aminoacid intake. A high carbohydrate, low protein diet was shown to improve cardiovascular health and extend lifespan, but did however increase body fat and caloric intake. A recent analysis by the National Health and Nutrition Examination Survey (NHANES) also showed a reduction in overall mortality in people younger than 65 years old under a low protein diet. Moreover, just restrincting a single amino-acid in a normal diet has been proved to increase lifespan and stress resistance. For instance, lab rodents with a methionine restricted diet showed extended health- and lifespan, as well as an increased resistance to oxidative stress, whereas a tryptophan-restricted diet also reduced age-dependent diseases and promoted longevity.
Lastly, other than limiting caloric intake, in one way or another, we can act over the feeding schedule, which has been shown to have a strong influence on health and survival, probably due to the circadian nature of proteins like sirtuins, strongly involved in aging-feeding related metabolism. In mice, restricting access to food to 8-9 hours of their active phase induced a reduction of metabolic diseases even in absence of a lowering of caloric intake, what’s more, this restricted feeding schedule reversed the progression of pre-existing obesity and type II diabetes. In this line of thought there’s reseach that shows that the daily eating schedule influences weight gain/loss, thus confirming the importance of the circadian rythm over the energy metabolism.
All these alternative models to caloric restriction hold promise for the treatment and prevention of metabolic diseases and might be beneficial in promoting healthy aging without the negative implications of a strons caloric restriction. However, more research is needed in order to confirm the validity of the experimental results in animal models before extrapolating to humans.