Luc Tappy, contributor
(Image: Martin Parr/Magnum)
In Fat Chance, endocrinologist Robert Lustig argues that insidious changes to our eating habits have caused disruptions to our endocrine systems
THE number of obese people in the world has doubled in the last three decades. During the same period, the way we eat has changed insidiously: the proportion of meals eaten outside the home has grown, people have come to rely more and more on ready-to-eat processed foods, and sugar consumption has soared to the highest levels in human history. Unsurprisingly, none of this is for the better of our health, says endocrinologist Robert Lustig.
Obese people struggling to lose weight, and health professionals involved in helping them to do so, will agree that obesity is not down to mere gluttony or sloth. Subtle, yet unrecognised neuroendocrine defects likely also play a role.
In Fat Chance, Lustig argues that the rise of obesity is the result of high concentrations of insulin in the blood, together with resistance to leptin - a hormone secreted by the body's fat cells that normally signals the brain to shut down food intake.
According to his hypothesis, the problem begins when dietary sugar stimulates insulin secretion, promoting storage of food energy in fat cells. Because this energy is not available to other cells, the signal to eat doesn't get switched off. In such conditions, leptin should tell the brain to reduce food intake. But the brains of obese people who have developed insulin resistance also become resistant to the effects of leptin. Lustig says that is because high insulin levels block leptin's signals to the brain, but unfortunately he doesn't show by what mechanism this might be happening, or clarify whether leptin resistance is a direct consequence of eating sugar. Still, if these factors are at work, it would help to explain uninhibited overeating.
After laying out his theory, Lustig goes on to scrutinise the composition of the average modern diet. He concludes that four specific nutrients are instrumental in the development of obesity. Top of the list are "sugars", and more specifically fructose. This monosaccharide is consumed when foods contain added sugar (be it cane or beet sugar, or high-fructose corn syrup). Fructose, which Lustig describes as a toxin, can be converted into fat by the liver, and hence can be directly involved in the development of complications of obesity such as heart disease and non-alcoholic fatty liver disease. The other three nutrients on his hazards list are alcohol, branched-chain amino acids and trans fats.
Once he has made a case for the causes of obesity, Lustig outlines the dietary changes and public policies required to reduce them. These are very familiar: a drastic reduction in sugar consumption, increasing intake of foods that contain high amounts of dietary fibre - whole fruits rather than juices, for example - and an increase in physical activity.
There are many books on the ills of obesity. So what does this one add? Fat Chance is certainly not intended as a practical guide for people attempting to lose weight, and with often superficial presentations of the science, it is not for health professionals either. Instead, this book offers the general reader a critical appraisal of our present diet and eating habits. Most important, Lustig's recommendations to reduce sugar intake, eat more fibre-rich foods, and lobby the food industry and government to take practical steps to improve the quality of our diet, are certainly valid and more than appropriate.
Fat Chance is a position statement. Lustig argues that sugar and processed foods are driving the obesity epidemic, and he calls for policy interventions to reduce their consumption by any possible means. He is venturing into controversial territory and many of his hypotheses remain unproven, and at times draw on a rather thin scientific background. Yet they are nonetheless highly plausible - and worrying.
Luc Tappy is a professor of physiology at the University of Lausanne in Switzerland
Fat Chance: Beating the odds against sugar, processed food, obesity, and disease by Robert H. Lustig
Fourth Estate/Hudson Street Press
£13.99/$25.95
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