‘Demonising’ single nutrients hinders fight against obesity

That’s the view of David Raubenheimer and Stephen Simpson, both professors at the University of Sydney's Charles Perkins Centre, who say existing models for measuring health impacts of the human diet are outdated and restrictive.

They insist the single-nutrient model, which has been so successful in dealing with micronutrient-deficiency diseases, has clearly failed in relation to obesity. 

In the latest edition of Annual Review of Nutrition​​, they call for a rethink of human nutrition science through a new framework called “nutritional geometry​”, which considers how mixtures of nutrients and other dietary components influence health and disease, rather than focusing on any one nutrient in isolation. 

"Our framework throws down the gauntlet to the whole field of human nutrition. It shows that the prevailing focus on single nutrients is not able to help us understand complex chronic diseases, and that an approach based on nutrient balance can help solve the problem," ​said Prof. Simpson.

Savvy marketing​

Instead, the scientists believe modern nutrition-related diseases are driven by an overabundance of food, an evolved fondness for foods containing particular blends of nutrients, and “savvy marketing by the packaged-food industry”. ​

"Conventional thinking which demonises fat, carbohydrate or sugar in isolation as causes of the obesity crisis—dubbed the single nutrient approach—has now run its course. We've provided a framework for not only thinking about but also experimentally testing issues around dietary balance. Much like the invention of the telescope or microscope, this framework offers a new tool with which to look at complex dietary problems and bring them into focus,"​ said Prof. Simpson.

"Our new approach provides a unique method to unify observations from many fields and better understand how nutrients, foods and diets interact to affect health and disease in humans​," added Prof. Raubenheimer.

"The nutritional geometry framework enables us to plot foods, meals, diets and dietary patterns together based on their nutrient composition, and this helps researchers to observe otherwise overlooked patterns in the links between certain diets, health and disease."​

The new model enables complex problems like obesity to be viewed from a variety of perspectives, from the impacts of nutrients on metabolism and the health of individuals, through to the sustainability of global food systems.

Simplify study​

"Although at face value more complex than the single-nutrient model, our framework can simplify the study of human nutrition in the long-run by helping to identify those subsets of factors and their interactions that are driving negative health and environmental outcomes in our rapidly changing environments,"​ said Prof. Simpson. 

To illustrate the approach, Raubenheimer and Simpson plotted data for the composition of 116 diets, compiled from previous published studies examining macronutrient ratios of carbohydrate, fats and protein, and energy intake in humans.

Their model shows that protein was the strongest driver influencing diet, regulating the intake of fat and carbohydrate. They say this finding is consistent with the previously observed "protein leverage"​​ phenomenon, in which the strong human appetite for protein leverages the intake of fats, carbohydrates and total energy. 

Source: Annual Review of Nutrition​
Vol. 36: 603-626, DOI: 10.1146/annurev-nutr-071715-051118
“Nutritional Ecology and Human Health”​
Authors: David Raubenheimer and Stephen J. Simpson