New dieting secrets to long life

Rhesus monkeys in University of Wisconsin calorie-restriction diet trial… Canto, 27 (left), on a restricted diet, and Owen, 29 (right), on an unrestricted diet – Photo by Jeff Miller

Rhesus monkeys in University of Wisconsin calorie-restriction diet trial… Canto, 27 (left), on a restricted diet, and Owen, 29 (right), on an unrestricted diet – Photo by Jeff Miller

CUTTING calories through dietary restriction has been shown to lower cholesterol, improve insulin sensitivity, and even prolong life in mammals. Now, new research publishing on May 28th in Cell Reports shows that, at least in mice, low protein, high carbohydrate diets can provide benefits similar to those obtained with calorie restriction.

“We’ve shown that when compared head-to-head, mice got the same benefits from a low protein, high carbohydrate diet as a 40 per cent caloric restriction diet,” says senior author Stephen Simpson, Academic Director of the University of Sydney’s Charles Perkins Centre. “Except for the fanatical few, no one can maintain a 40 per cent caloric reduction in the long term, and doing so can risk loss of bone mass, libido, and fertility.”

The investigators compared three eight-week diets varying in protein-to-carbohydrate ratio under conditions where food was restricted or food was available at all times. Of the three, low protein, high carbohydrate (LPHC) diets offered when food was always available delivered similar benefits as calorie restriction in terms of insulin, blood sugar, and cholesterol levels, despite increased food intake.

Even though the mice on LPHC diets ate more when food was always available, their metabolism was higher than that of mice on the calorie-restricted diet, and they did not gain more weight. Calorie restriction did not provide any additional benefits for LPHC mice.

Additional research is needed to determine how LPHC diets affect long-term metabolic health and survival, as well as to what extent the type and quality of proteins and carbohydrates matter. “An important next step will be to determine exactly how specific amino acids, the building blocks of proteins, contribute to overall health span and lifespan,” says lead author Samantha Solon-Biet, also of the Charles Perkins Centre.

If the study’s results apply to humans, adjusting protein and carbohydrate intake could lead to healthier aging in a more realistic manner than drastically cutting calories. “It still holds true that reducing food intake and body weight improves metabolic health and reduces the risk of diseases like type 2 diabetes, obesity, and fatty liver disease,” says Simpson. “However, according to these mouse data and emerging human research, it appears that including modest intakes of high-quality protein and plenty of healthy carbohydrates in the diet will be beneficial for health as we age.”

In an earlier study by the University of Wisconsin, United States, 76 rhesus monkeys were split into two groups, the control group fed on a normal diet whilst the test group is fed on a diet of 30 per cent less calories. At an older age those in the calorie restricted test group displayed a more youthful and healthy appearance whilst monkeys from the control group appeared much less healthy and less energetic. A previous study from 1987 by the National Institute on Ageing also on rhesus monkeys found evidence of health benefits but no evidence of increased median lifespan.
Can eating less extend your life?

Reducing calorific consumption has been a key consideration in health nutrition for as long as the study has existed and for as long as we have had an abundance of food to eat. When people decide to reduce the numberof calories they consume the reason is almost always to lose weight.

Several studies have shown that the motivation for this can be to improve outward physical appearance, improving day to day health and even to avoid an early death due to conditions such as obesity and type-2 diabetes. However there may be an additional and much greater benefit in reducing the amount of calories that we consume as it may enable us to live and remain healthier for longer.

Since the 1980s researchers have been conducting an experiment on rhesus monkeys by restricting their calories to see if calorie restriction is beneficial in improving their health and ultimately slowing down ageing, as it does in other species such as yeast, worms, flies, spiders, rats, mice, dogs, cows, among others the diet has been tested on. Rhesus monkeys live around 27 years on average, and are thought to be the most similar physiologically to humans — so it’s believed the results would be more translatable to humans.

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