Diet fads often make the lofty claim that adjusting food habits one way or another will produce the dieter's desired results. More specifically: Eat this, not that, and watch the kilos fall off. But diets are hard to sustain, and it seems like diet debunking is constantly calling into question what and how much we should be eating.
In a review published this week in the new issue of Science, scientists from diverse backgrounds and research focuses came together to address whether a high-fat, low-carbohydrate diet or vice versa was the better option for maintaining good health, as well as whether the specific kinds of fat and carbs mattered.
The researchers — from the Harvard T. H. Chan School of Public Health, Boston Children's Hospital, Ohio State University, and others — hoped that by comparing their knowledge of nutrition, they could both find general areas of agreement and identify others where more research is needed in an effort to the end the so-called "diet wars."
While their respective areas of research and knowledge meant that they differed in their positions on what defined the perfect diet for obesity treatment and chronic disease prevention — including the oh-so-hyped ketogenic diets — they did agree on several key points.
First, the quality of diet matters; the researchers stated that in focusing on nutrient quality, "good health and low chronic disease risk can be achieved for many people on diets with a broad range of carbohydrate-to-fat ratios."
Overall, everyone benefits from swapping saturated fats for naturally occurring unsaturated fats, or stuff like avocado, nuts, and seeds. They also agreed folks are better off reaching for unprocessed carbohydrates like non-starchy vegetables, whole fruits, and whole or minimally processed grains than processed carbohydrates. Trans fats, which are found in stuff like baked goods and fried food, should be totally cut out of any diet. (But you already knew that.)
Researchers also agreed that biological factors could impact how certain individuals responded to different kinds of diets, so the perfect diet isn't necessarily a one-size-fits-all answer.
"This is a model for how we can transcend the diet wars," David Ludwig, a professor in the Department of Nutrition at Harvard Chan School and lead author on the study, said in a statement. "Our goal was to assemble a team with different areas of expertise and contrasting views, and to identify areas of agreement without glossing over differences."
Some things the researchers were conflicted about included possible advantages of ketogenic diets, such as whether they provide "metabolic benefits beyond those of moderate carbohydrate restriction." They also said more research is needed to determine keto's success in treatment for diabetes, its health effects generally, as well as its long-term sustainability and potential environmental toll.
The study authors did agree, however, that low-carb diets don't necessarily require the consumption of a ton of meat.
"Well-formulated low-carbohydrate, high-fat diets do not require high intakes of protein or animal products," the authors wrote. "Reduced carbohydrate consumption can be achieved by substituting grains, starchy vegetables, and sugars with non-hydrogenated plant oils, nuts, seeds, avocado, and other high-fat plant foods."
The general takeaway appears to fall in line with what your mum probably told you as a kid: Eat your fruits and veggies, keep the processed foods to a minimum (or cut them altogether), and curb the sugar. If you're doing that, you're probably doing alright.