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Nutrition scientists are battling over what we should eat. This is what they agree on

By Sam Downing| 2 weeks ago

 

Last week a team of nutrition scientists published the results of a study that suggested maintaining weight loss may be easier on a low-carb diet.

It's the latest entry in a heated war between nutrition scientists: one faction advocates low carb intake (20 percent or less of your daily energy from carbohydrates, with most of the remaining 80 percent coming from fat); and another advocates more moderate carb intake (between 45 and 65 of energy from carbohydrates — the amount prescribed by Australian government health authorities).

Both factions are headed by renowned scientists from lofty institutions, and backed by compelling science — which leaves us everyday bystanders wondering what, exactly, we're supposed to eat.

A follow-up paper published in the journal Science offers some answers

It seeks to overcome the so-called "diet wars" by gathering US nutrition rivals and uncovering what food rules they agree on, and canvassing studies that support both lower- and higher-carb diets.

Despite the complexities of the carbohydrate-fat war, the paper's outcome is pretty simple.

First, there's no specific ratio of carbs to fat that works best for everyone, so it will never be possible to declare a winning diet.

"Good health and low chronic disease risk can be achieved for many people on diets with a broad range of carbohydrate-to-fat ratios," wrote the paper's authors, who include Harvard nutrition professors David Ludwig (who favours a low-carb approach) and Walter Willett (who favours a moderate-carb approach).

RELATED: What's the best diet? It depends how you define 'diet'

Second, the sources of carbs and fats matters as much, or even more than, the ratio you eat them in. Or, to put it even more simply: just eat whole, high-quality foods. 

Both sides agree on limiting highly processed carbs, including refined grains, potato products, and free sugars — such as confectionary, soft drink, fruit juice and foods with sugar added my manufacturers.

Those highly processed carbs should be replaced by unprocessed carbohydrates, such as non-starchy vegetables, whole fruit, beans and other legumes, and whole grains — think brown bread, pasta and rice.

Those who do opt for low-carb, high-fat diets should swap carbohydrates with the healthier fats found in the likes of non-hydrogenated plant oils (eg, olive oil, sunflower oil and canola oil), nuts, seeds and avocado.

In other words, don't pile up on bacon: the paper's authors agreed that, on the whole, saturated fats should be replaced by unsaturated fats, and that trans fats should be eliminated altogether.

However, the paper did note that more research is needed into saturated fat — which has long been pegged as "bad" fat,  though other research indicates it's not that simple.

RELATED: Don't fear dairy, study concludes — but don't rush to pig out on it, either

More research is also needed into the ketogenic diet, characterised by very high amounts of fat (70 percent or more of dietary intake from fat) and very low amounts of carbohydrate. Most health experts warn that this diet is not suitable for the general population — it's not only hard to follow, but may have unintended health consequences — but the authors of the new paper agreed it may have therapeutic uses for specific conditions.

"More research needed" is, in fact, one of the paper's major conclusions.

"Currently, the United States invests a fraction of a cent on nutrition research for each dollar spent on treatment of diet-related chronic disease," write the authors.

"Given the enormous human and economic toll of diet-related disease, high-quality research into key controversies should be given priority."