Food and Behaviour Research

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Scientists claim that overeating is not the primary cause of obesity

American Society for Nutrition


Could the carbohydrate-insulin model point the way to more effective, long-lasting weight management strategies?


For decades, we've all been told that to lose weight, you simply need to 'eat less and exercise more' - because it's all about the 'calories in, versus calories out'.

But research shows that unless you cut the sugar and refined carbs - NOT JUST the calories - the effects of these on your metabolism, energy levels, appetite and mood are almost guaranteed to set you up to fail (as the real world evidence shows). And miserably so, as you'll be blamed for your own 'lack of willpower'.

The key issue is that a high-sugar diet will rob you of energy (because it increases the proportion of calories stored as fat), and will make you feel hungry (because of associated changes in brain signalling systems). Then you'll get called 'lazy' and 'greedy'.... (because of course it must all be your fault.)

Evidence shows that weight gain, or loss, depends on WHAT KINDS OF FOODS we eat - not just their calorie content. 

The proposal here from 17 leading scientists that diets high in sugar - and other refined carbohydrates that release sugar quickly - lead to hormonal and metabolic changes that promote obesity, Type 2 diabetes and other health-damaging metabolic conditions is not new.

Its highly distinguished supporters include Professor Robert Lustig - author of the recent book ‘Metabolical’, and a leading researcher and medical expert in obesity and endocrinology, and other leading scientists allied with the campaign group Action on Sugar.

In 2006, Lustig published a key article explaining the failures of a focus on calories alone to control obesity. 

Decades ago, the leading UK scientist John Yudkin flagged the potential dangers of sugar (not fat) in his pioneering book ‘Pure, White and Deadly’. And decades before that, the distinguished medical doctor T.L. Cleave had already concluded that diets high in sugar and refined carbohydrates were a key factor increasing risks for most non-communicable diseases.

Public health authorities really need to start taking the scientific evidence on board, improving their messaging to warn the public, and educating heath professionals more on the negative effects of ultra-processed, high-sugar diets. 

Otherwise, the ongoing pandemic of obesity, Type 2 diabetes and other metabolic diseases will continue (along with the related epidemic of eating disorders and associated mental health problems) while the ultra-processed food and 'diet & weight-loss' industries keep laughing all the way to the bank.

For the related research article please see:

For further information about this topic please see:

13/09/2021 - Medical Xpress

Statistics from the Centers for Disease Control and Prevention (CDC) show that obesity affects more than 40% of American adults, placing them at higher risk for heart disease, stroke, type 2 diabetes, and certain types of cancer. The USDA's Dietary Guidelines for Americans 2020—2025 further tells us that losing weight "requires adults to reduce the number of calories they get from foods and beverages and increase the amount expended through physical activity."
This approach to weight management is based on the century-old energy balance model which states that weight gain is caused by consuming more energy than we expend. In today's world, surrounded by highly palatable, heavily marketed, cheap processed foods, it's easy for people to eat more calories than they need, an imbalance that is further exacerbated by today's sedentary lifestyles.

By this thinking, overeating, coupled with insufficient physical activity, is driving the obesity epidemic. On the other hand, despite decades of public health messaging exhorting people to eat less and exercise more, rates of obesity and obesity-related diseases have steadily risen.
The authors of "The Carbohydrate-Insulin Model: A Physiological Perspective on the Obesity Pandemic," a perspective published in The American Journal of Clinical Nutrition, point to fundamental flaws in the energy balance model, arguing that an alternate model, the carbohydrate-insulin model, better explains obesity and weight gain. Moreover, the carbohydrate-insulin model points the way to more effective, long-lasting weight management strategies.
According to lead author Dr. David Ludwig, Endocrinologist at Boston Children's Hospital and Professor at Harvard Medical School, the energy balance model doesn't help us understand the biological causes of weight gain: "During a growth spurt, for instance, adolescents may increase food intake by 1,000 calories a day. But does their overeating cause the growth spurt or does the growth spurt cause the adolescent to get hungry and overeat?"
In contrast to the energy balance model, the carbohydrate-insulin model makes a bold claim: overeating isn't the main cause of obesity.

Instead, the carbohydrate-insulin model lays much of the blame for the current obesity epidemic on modern dietary patterns characterized by excessive consumption of foods with a high glycemic load: in particular, processed, rapidly digestible carbohydrates. These foods cause hormonal responses that fundamentally change our metabolism, driving fat storage, weight gain, and obesity.
When we eat highly processed carbohydrates, the body increases insulin secretion and suppresses glucagon secretion. This, in turn, signals fat cells to store more calories, leaving fewer calories available to fuel muscles and other metabolically active tissues.

The brain perceives that the body isn't getting enough energy, which, in turn, leads to feelings of hunger. In addition, metabolism may slow down in the body's attempt to conserve fuel. Thus, we tend to remain hungry, even as we continue to gain excess fat.
To understand the obesity epidemic, we need to consider not only how much we're eating, but also how the foods we eat affect our hormones and metabolism. With its assertion that all calories are alike to the body, the energy balance model misses this critical piece of the puzzle.
While the carbohydrate-insulin model is not new—its origins date to the early 1900s—The American Journal of Clinical Nutrition perspective is the most comprehensive formulation of this model to date, authored by a team of 17 internationally recognized scientists, clinical researchers, and public health experts. Collectively, they have summarized the growing body of evidence in support of the carbohydrate-insulin model. Moreover, the authors have identified a series of testable hypotheses that distinguish the two models to guide future research.
Adoption of the carbohydrate-insulin model over the energy-balance model has radical implications for weight management and obesity treatment. Rather than urge people to eat less, a strategy which usually doesn't work in the long run, the carbohydrate-insulin model suggests another path that focuses more on what we eat.

According to Dr. Ludwig, "reducing consumption of the rapidly digestible carbohydrates that flooded the food supply during the low-fat diet era lessens the underlying drive to store body fat. As a result, people may lose weight with less hunger and struggle."
The authors acknowledge that further research is needed to conclusively test both models and, perhaps, to generate new models that better fit the evidence. Toward this end, they call for constructive discourse and "collaborations among scientists with diverse viewpoints to test predictions in rigorous and unbiased research."