Food and Behaviour Research

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The carbohydrate-insulin model: a physiological perspective on the obesity pandemic

Ludwig D, Aronne L, Astrup A, Cabo R, Cantley L, Friedman M, Heymsfield S, Johnson J, King J, Krauss R, Lieberman D, Taubes G, Volek J, Westman E, Willett W, Yancy W, Ebbeling C (2021) The American Journal of Clinical Nutrition  Sep 13;nqab270 doi: 10.1093/ajcn/nqab270 

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Abstract:

According to a commonly held view, the obesity pandemic is caused by overconsumption of modern, highly palatable, energy-dense processed foods, exacerbated by a sedentary lifestyle. However, obesity rates remain at historic highs, despite a persistent focus on eating less and moving more, as guided by the energy balance model (EBM).

This public health failure may arise from a fundamental limitation of the EBM itself. Conceptualizing obesity as a disorder of energy balance restates a principle of physics without considering the biological mechanisms that promote weight gain.

An alternative paradigm, the carbohydrate-insulin model (CIM), proposes a reversal of causal direction. According to the CIM, increasing fat deposition in the body-resulting from the hormonal responses to a high-glycemic-load diet-drives positive energy balance.

The CIM provides a conceptual framework with testable hypotheses for how various modifiable factors influence energy balance and fat storage.

Rigorous research is needed to compare the validity of these 2 models, which have substantially different implications for obesity management, and to generate new models that best encompass the evidence.

FAB RESEARCH COMMENT:

For decades, obesity has been regarded primarily as a disorder of 'energy balance' (calories in > calories out).

Accordingly, campaigns based on 'eating less, and moving more' have formed the basis of public health initiatives, commercial 'weight-loss' plans, and the private efforts of individuals to combat obesity.

Unfortunately, this approach has completely failed to stem the pandemic of obesity and related metabolic conditions (such as diabetes and cardiovascular disease), indicating that different approaches are needed.


An alternative to the 'energy balance' model - the carbohydrate-insulin model (CIM) - has been gaining ground for many years amoung many scientists and medical practitioners.  This focuses not on total calories in or out, but instead on the actual biological mechanisms that promote weight gain. 

In this model, hormonal responses to a high-sugar diet cause an obligatory increase in fat storage, so that correspondingly fewer calories are available to be burned for energy.  Increased appetite, and reduced energy levels then follow from these hormonal changes - and this in turn drives 'positive energy balance' - i.e. eating more, and moving less.

As these authors emphasise - more research is still needed to put this approach to the test - but that need is urgent now, as the implications for public health practice could hardly be more important.


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