Adapted from paper by Dr David S Ludwig and Dr Jens J Holst published in JAMA May 1 2023
Treatment that focuses on the root cause of a disease has guided research and clinical practice for centuries. The American Academy of Pediatrics (AAP) published a clinical practice guideline for the evaluation and treatment of children with obesity earlier this year. This guideline emphasises the use of weight loss drugs and bariatic surgery. Diet received little attention apart from advising the USDA’s MyPlate recommendations and the limitation of sugar sweetened beverages.
The researchers are of course constrained by available evidence and the results on weight loss for drugs and surgery do seem superior to the changes achieved by diet. Yet, the physiological changes that occur on a carbohydrate restricted diet have many similarities to what occurs in the body with drugs such as GLP-1 receptor antagonists.
GLP-1 RAs improve beta cell sensitivity to glucose so that the same amount of insulin will be released at a lower glucose concentration. It also slows the rate that the stomach empties after eating food. Thus people feel fuller up after eating for longer, and the lower blood sugars released from the stomach over time result in lowering the total amount of insulin from the pancreas. The lower the rate that the stomach empties, the more weight is lost.
Slower digesting carbohydrate, for instance, must travel farther down the gut before being fully absorbed. This causes lower post meal blood sugars and insulin secretion. Protein and fat also digest more slowly and stimulate less insulin secretion than an equivalent amount of rapidly absorbed carbohydrate. Additional similarities between low glycaemic load diets and GLP-1 RAs include lower leptin levels, suggesting lower leptin resistance, lower ghrelin levels and higher adiponectin levels. This dietary strategy shares mechanisms with gastric bypass surgery which shifts nutrient absorption from a more proximal to a more distal location in the intestines. Of special relevance is that natural GLP-1 secretion is increased with a low glycaemic load diet, which slows gastric emptying thus improving satiety, and bariatric surgery.
Although in theory a low carb diet should be able to replicate the results of GLP-1 RAs (15% weight loss) results are usually disappointing, except where a ketogenic diet with intensive behavioural support (12% weight loss) is provided. In other words, the results can be almost replicated but the person must stick to the diet.
GLP-1 RAs cost $1,400 per adolescent per month. Treatment of all adults with obesity would cost $1 trillion and all adolescents $100 billion per year. Instead of spending this sort of money to solve the obesity crisis, it would be more worthwhile to enhance dietary quality and create environments that would encourage physical activities and outdoor play as an alternative to screen time and electronic gadgets. This would improve mental as well as physical health.
Unfortunately, once GLP-1 RAs are stopped, the weight is usually rapidly regained. Therefore we are really looking at potentially lifelong drug treatment for the obese population. We do not know the effects of prolonged drug treatment on other health factors. A low quality diet could still produce a raised lifetime risk of cardiovascular disease, cancer and other chronic conditions, independent of weight.
Perhaps low glycaemic load diets when given in conjunction with GLP-1 RAs would improve the therapeutic effect and thus allow drug use at lower dosages. This could reduce adverse effects.
To advance science and social justice we must fund research into new dietary treatments and overcome obstacles to the provision of intensive behavioural interventions. Especially for children, diet and lifestyle must remain at the forefront of obesity prevention and treatment.
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