Cut calories. Slow biological ageing

The cutting edge of nutrition science is seeing a quiet revolution as the scientific community increasingly uncovers the deep linkages between nutrition and human health, and public health agencies initiate programs such as the "Food is Medicine" initiative of the US Government. One interesting finding of nutrition science is that reducing calorie intakes slows ageing at the cellular / genetic level, and can potentially have a far-reaching impact on longevity and healthy ageing.


Low calorie diets and longevity

A National Geographic journalist and explorer, Dan Buettner, led an exploratory project in 2004 to identify and study micro-regions in the world characterized by noticeably high longevity and health in longevity compared with other sub-regions in similar geographies. The study identified 5 micro-regions spanning 4 continents – Ikaria in Greece, Sardinia in Italy, Loma Linda in the US, Okinawa in Japan, and Nicoya in Costa Rica – where lives were both significantly longer and healthier. For example, at least one-third of Ikaria’s residents live past 90 years; and the region is substantially dementia-free.

There are several factors that are found to contribute to healthy longevity in these regions – physical activity, social relationships, and diets that are vegetarian-centric and emphasize minimally processed foods. One of the shared characteristics across all of these micro-regions: low caloric intake. The average male adult in these regions sustains on a diet of 1,800 kCal in spite of maintaining an active lifestyle – this nutritional intake is almost 25% lower than that recommended under the US’ Dietary Guidelines for Americans.


Scientific research on calorie-restricted diets and their impact on ageing

The first bits of evidence of calorie intake and its impact on ageing was found in 1935, when a researcher in Cornell University discovered that rats on a calorie-restricted diet lived nearly 30% longer lives than rats on a ‘normal’ diet. Since this finding, scientists have been running experiments on a wide variety of animals, to understand this linkage better.

Since then, multiple studies have validated the linkage between caloric reduction and the inhibition of biological ageing across a variety of species, including rats, mice, dogs, and monkeys. Some studies extrapolated the findings from this research to human lifespan extension. For example, a 1990 research paper estimated that caloric reduction could increase the lifespan of the average 50-year-old American woman from an expected 82 years to 112 years, adding 30 years.

To put this in perspective, simultaneously curing cancer, cardiac disease, stroke and diabetes was estimated in the same study to increase life expectancy by only 14 years. This makes caloric reduction potentially more beneficial for healthy ageing and longevity than curing four of the leading causes of mortality – a powerful thesis indeed!

It was not until very recently that scientific studies to establish the linkage between caloric reduction and ageing were finally carried out in humans. Researchers at group of US universities published a paper in 2015 following a 2-year experiment to examine the effects of caloric reduction on ageing at the level of the cell, carried out on healthy adults. Biological ageing of these subjects was measured by measuring DNA methylation (a molecular process associated with ageing) from blood samples. A 25% reduction in calories was found to slow ageing by 2-3%. Over a lifetime, the compounding effect of this seemingly minor reduction in ageing rates can translate into more than a decade of additional lifespan.


Other health benefits of a low-calorie diet

Low calorie diets not only slow down biological ageing; individuals with lower rates of biological ageing also exhibit many of the health benefits associated with ‘youth’:

  • Lower risk of chronic disease development
  • Higher physical functioning
  • Higher mental functioning

Calorie-reduced diets therefore not only support longer life; they also enable healthier living in spite of advanced chronological age.


Key principles of beneficial Caloric Reduction

  • Caloric Reduction for ageing benefits requires the sustained reduction of dietary energy – for periods running into at least 18-24 months – as compared with energy requirement for weight maintenance.
  • Optimal calorie reduction yields benefits for ageing, while minimizing potential harm to physical fitness (e.g., malnutrition, chronic weakness, reduced aerobic capacity) and mental well-being (emotional distress, confusion, depression, etc.)
    • Diets with calorie reduction of 10-30% over the baseline have been found to show the maximum benefits with respect to ageing parameters, without compromising on physical and mental well-being
    • Diets where calorie reduction has exceeded 40% have been linked to physical and mental disorders, such as fertility and sexual health, immunity, fatigue. This partly arises because such diets are often also associated with shortfalls in nutritional intakes.
  • When reducing calories, ensure nutritional quality is maintained – e.g., the diet needs to be rich in micronutrients, fiber, and antioxidants; while maintaining a healthy balance of macronutrients.


Practical tips to achieve Caloric Reduction

Caloric reduction can be practically achieved in a number of ways:

  • Conventional calorie reduction: Reduce calorie intake for each meal consumed – i.e., reducing portion sizes
  • Intermittent Fasting: The practice of not eating at all for a significant part of the day, for example 14-10 (14 hours of fasting combined with 10 hours during which meals are consumed, limiting total calories according to the calorie reduction plan). Intermittent fasting works because in a few hours after food consumption, the body exhausts its sugar stores and starts burning through fat. After an initial 2-4 week adjustment period, the body gets used to the meal timing patterns, and in fact the stomach shrinks to demand less food per meal.
  • Time-restricted eating: While similar to intermittent fasting, the key construct behind time-restricted eating involves aligning dietary intake to the body’s energy needs during various parts of the day. This means, for example, eating early and light dinners, and concentrating one’s calorie intake during the morning and early afternoon periods.


In conclusion, caloric reduction can be a powerful tool available to healthy individuals to slow down ageing processes and for healthy ageing. Do consult your doctor and perhaps your nutritionist to help you design your own caloric reduction plan.

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