Even as the saturated fat and coronary disease association is being fiercely debated, particularly in the UK and the US, in India, the diet-heart association is not so much around the role of saturated fats. Instead, we need to trace the rising obesity levels to factors such as maternal nutrition, says Dr K. Srinath Reddy, eminent cardiologist and former president of the World Heart Federation. Reddy says there is enough evidence of the association between under-nutrition and the subsequent predisposition to non-communicable diseases (NCDs) such as heart disease and diabetes. Reddy, also director of the Public Health Foundation of India (PHFI), points to the thrifty phenotype theory—or reduced foetal growth and its association with diseases later in life—that explains the rising rate of obesity, and our susceptibility to NCDs.
“In the west, the debates around fat and heart disease revolve around their fatty diets, and a subsequent replacement of saturated fats with unhealthy, refined carbs that led to a rise in coronary heart disease. In India, that is not so much the concern. We do, however, need to be concerned about the rising rates of coronary heart disease and other NCDs, that can be traced to what our mothers were eating, and the kind of ultra-processed, unhealthy food we are increasingly consuming,” he says. Low birth-weight and early exposure to under-nutrition—especially between two to six years—translates into rebound adiposity [body fat increases at the expense of lean muscle mass, as a result of physiologic mismatch between early life malnutrition and later diet]. The body's metabolism adapts to low nutrition in early life, and later, a high carbohydrate diet gives rise to higher fat deposition especially in the abdomen, and a high waist-hip ratio, says Reddy. “While there is no evidence for a genetic predisposition to these diseases, an epigenetic effect [altered gene expression] does play a role in the rising burden of coronary heart disease, apart from factors such as low physical activity and increased intake of refined carbohydrates,” he adds.
While our genes themselves may not place us at a disadvantage when it comes to storing fats, environmental factors do contribute to an increased expression of certain genes, he says. A PHFI study showed that urban migrants had higher levels of risk factors such as high blood pressure and low density lipoproteins than their rural siblings. “This shows how much the environment shapes the expression of certain genes. In an urban setting, even factors such as air pollution will come into play,” he says.
Though studies in favour of saturated fat, and the deleterious effect of refined carbohydrates on increasing disease burden have a global significance, Reddy says that when it comes to nutrition science, a reductionist approach leads to an understanding in terms of individual foods, or single molecules. “This approach leads to contradictory evidence, and confusion. So eggs are bad, and then they are good; dairy is bad, and then it is good; coconut oil that was once not good, is now not so bad; and so on. Instead, it would help our understanding if we focused on composite dietary patterns, and the interaction of different molecules,” he says. For instance, research has found that the Mediterranean diet—high on healthy fats—has a protective effect on coronary heart disease, whereas the low-fat Japanese diet has also been found to promote higher life expectancy.
Each nutrient, whether it be fat, protein, or carbohydrate, cannot be considered in isolation. “Each food item contains several nutrients which interact, supplement or counteract each other’s effects. Similarly, a single food item cannot be considered in isolation since food items modify each other's effect in a normal diet,” says Reddy, who advocates the principle of dietary diversity. Diversity is important since it provides a balance of nutrients through a variety of food items. “Of course harmful components like refined carbohydrates and trans-fat must be greatly reduced and salt must be consumed in moderation. This can be done by avoiding ultra-processed foods,” he says.