A low-protein, high-carbohydrate diet can protect middle-aged people from heart disease and type 2 diabetes as much as reducing their calorie intake by 40 per cent, a new mouse study suggests.
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But, warn the authors, it's all about eating the right kind of carbohydrates, such as brown rice and fibre-rich fruit and vegetables.
"We're not talking about eating sugar," says nutritional ecologist Professor Stephen Simpson of the University of Sydney.
It's been long known that restricting your calories by around 40 per cent is one way to boost your metabolic health -- the bodily processes that help protect you against type 2 diabetes and cardiovascular disease as you get older.
But restricting your calories by this much can be quite miserable and can have negative side effects on bone mass, libido and fertility, says Simpson.
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"A 40 per cent calorie-restriction diet is impossible for most people," he says. "The 5:2 diet is very difficult for most people and that's nothing like 40 per cent."
"This study shows that by adjusting the macronutrient balance of your diet -- having the protein to carbohydrate ratio optimised -- you could get the same metabolic benefits."
Diet study
In today's issue of Cell Reports Simpson and colleagues report on a study in which they compared the effect of six different eight-week diets on middle-aged mice.
In three of the diets mice ate 40 per cent less than their normal calories, while in the other three, the animals were allowed to eat as much as they wanted (ad libitum).
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Both the calorie-restricted and ad libitum diets included three groups: high protein, low carbohydrate; medium protein, medium carbohydrate; and low protein, high carbohydrate.
During the study, the researchers measured how much food the mice ate, along with such things as insulin resistance, circulating lipids and cholesterol levels, to calculate the animals' metabolic health.
As expected, the mice on calorie restricted diets had the best metabolic health.
"But there were equally good outcomes for those on a low protein, high carbohydrate diet, allowed to eat as much as they liked," says Simpson.
High protein diets
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This is the first time that an ad libitum diet low in protein and high in carbohydrate has been found to have the same effect as calorie restriction, says Simpson.
He says that many high protein, low carb diets may help people lose weight or maximise fertility, but they could cause problems in the long term.
In his mouse study, the high-protein, low-carb diet was the worst for metabolic health.
Simpson says, while people with diabetes may need to reduce their carbohydrate intake, an average healthy, non-obese middle-aged person should not be too obsessed with counting calories and getting ultra thin.
Read more at ABC Science.