Researchers David Raubenheimer and Stephen Simpson for the University of Sydney say what they call “nutritionism”​ approaches have failed to combat the rise in obesity and associated cardiometabolic disease (OACD), in large because they lack an adequate framework to analyse human nutrition.

“We suggest that an important problem is that human nutrition science has uncritically retained the framework that guided its successes in combating diseases of micronutrient deficiency, which is in fundamental respects incompatible with the new suite of nutrition-related diseases​,” the researchers wrote in the Annual Review of Nutrition. ​

“Several authors have argued that the limited progress of nutrition science in dealing with OACD stems from its reductionist underpinnings: In emphasising specific nutrients, it fails to take into account the fact that food components interact in complex ways to give rise to emergent properties of diets that are not explicable at the level of individual chemical parts​,” they added.

Nutritional ecology approach​

Instead they suggest an approach based on 'nutritional ecology', which aims to look at systems as a whole without emphasising individual factors such as particular macronutrients like fats or carbohydrates.

“The field of nutritional ecology shares many of the challenges of human nutrition science, but it has developed within the fundamental theoretical framework of ecology and evolution (EE)​,” wrote the authors.

“Central to the EE framework is the premise that outcomes such as health and disease arise from the interaction between the animal and its environment. These interactions play out over a continuum of timescales, from short-term homeostatic responses to environmental variability, to the long-term process of natural selection driving adaptation through changes in population gene frequencies. ​

"Nutritional ecology, therefore, focuses not specifically on the organism or its environment, but rather on the dynamic interface between organism and environment​,” they continued.

Specifically, they suggest using what they describe as ‘nutritional geometry’, which looks at a number of nutritional factors in combination, based around appetite.

Raubenheimer and Simpson have previously developed the nutritional geometry framework in relation to insects, and later applied it to a number of different organisms, from slime moulds to primates, domesticated animals and humans.

Analysing appetite is key​

“[Our previous studies] illustrate how, by placing appetite at the centre of nutritional models, nutritional geometry can go a long way toward identifying the combinations of factors that animals integrate to optimise the process of foraging​,” the authors wrote.

“In particular, the questions of how appetites for different nutrients interact and how these interactions engage with the food environment to generate different patterns of nutrient intake have emerged as especially powerful guides for understanding animal nutrition.​”

To illustrate the nutritional geometry approach, the researchers used three-axis charts to represent how foods and meals combine fat, protein and carbohydrate.

They then used similar charts to plot other combinations of factors, in part using data from previous studies detailing 116 experimentally fixed diets which looked at energy intake.

This analysis suggested that energy intake was largely governed by protein.

“In humans, protein intake remains relatively constant, and consequently the intake of fat, carbohydrate, and therefore total energy varies passively with dietary protein concentration​.”

But the researchers also noted this was not an absolute relationship, and protein consumption could be influenced by high or low concentrations of carbohydrates and fats, but not to the same extent that carbohydrate or fat consumption was governed by protein availability.

“Nutritional geometry provides a way of implementing [deep biological] theories by modelling how nutrients interact with each other to produce the properties of foods and diets and how behavioural and physiological mechanisms engage with these interactions to influence health​,” wrote the authors.

“Although more complex than the single-nutrient model, in the long run this framework can simplify the study of human nutrition by helping to identify those subsets of factors and their interactions that are driving negative health outcomes in our rapidly changing environments.​”

Source: Annual Review of Nutrition​

Published online ahead of print, doi: 10.1146/annurev-nutr-071715-051118​​

“Nutritional Ecology And Human Health​”

Authors: Raubenheimer, D.; Simpson, S.J.