Is sugar or saturated fat responsible for obesity epidemic?
The alarm on sugar had been sounded already in 1972, when John Yudkin, a British professor of nutrition, published a booked called Pure, White and Deadly. He believed that sugar, not saturated fat, was the cause of life-threatening troubles such as obesity, heart disease and diabetes. This idea was not in line with that-time nutrition guidelines: his reputation was destroyed and he died in solitude in 1995.
The fat hypotesis
In 1980 the US government issued its first dietary guidelines after long consultation with America's most senior nutrition scientists.
The most prominent recommendation was to cut back on saturated fats and cholesterol.
The guidelines shaped doctors' dietary attitudes, food industry and the diets of several millions of people, who replaced steak and sausages with pasta and rice, butter with margarine and vegetable oils, eggs with muesli, milk with orange juice. But instead of becoming healthier, they grew fatter and sicker.
The health catastrophe
Since the late 1970s, the prevalence of obesity among adults more than doubled. According to the US Department of Health and Human Services, more than 2 in 3 adults and about 1/3 of children and adolescents are considered to be overweight or obese. At best, we can conclude that the official guidelines did not meet their goal. At worst, they might have led to a decades-long health catastrophe.
Ancel Keys was a nutritionist at the University of Minnesota, who introduced the so called 'fat hypotesis', an the idea that saturated fat from red meat, cheese, butter and eggs, raises cholesterol, which coagulates on the inside of coronary arteries, causing them to harden and narrow, until the flow of blood is prohibited and the heart seizes up. Based on the participation of 12,770 middle-aged men from 7 countries, Keys published a convincing monograph in 1970 which showed a correlation between intake of saturated fats and deaths from heart disease.
According to Yudkin, however, while humans have always been carnivorous, carbohydrates only became a major component of their diet 10,000 years ago, with the advent of mass agriculture. Sugar has been part of western diets for just 300 years. Saturated fats, by contrast, are bound up with our evolution: they are present even in breast milk. Anyhow, his reasoning fell on deaf ears, inspite of the fact that Keys' 7-country study had deficiencies: despite living on a diet rich in saturated fats, France and West Germany, two countries with relatively low rates of heart disease, had been left out from the study.
Years later, the study's lead Italian researcher, Alessandro Menotti found that the food that correlated most closely with deaths from heart disease was not saturated fat, but sugar. However, it was too late: the debate swung behind fat hypotesis and many years have passed until revision.
The UN's Food and Agriculture Organisation, in a 2008 analysis of all studies of the low-fat diet, found 'no probable or convincing evidence' that a high level of dietary fat causes heart disease or cancer.
Today, the US dietary guidelines 2015-2020 has the following recommendations in this regard:
- Consume less than 10 percent of calories per day from added sugars
- Consume less than 10 percent of calories per day from saturated fats
- Consume less than 2,300 mg per day of sodium