Researchers in Norway have found that elevated levels of saturated fat, as part of a very high-fat, low-carbohydrate (73% fat, 10% carb) diet (VHFLC), increase the health promoting form of cholesterol, HDL, without raising the harmful kind, LDL.
The topic of saturated fat continues to be contentious with this new randomised controlled trial, adding to a growing body of evidence that the diet-heart hypothesis from original research headed up by Ancel Keys is flawed.
The diet-heart hypothesis proposed that dietary saturated fat elevated blood cholesterol, and the latter drove heart disease mortality like nothing else.
The Norwegian study (FATFUNC), which compared the effects of VHFLC and a low fat, high carbohydrate diet on cholesterol after three months, found that both regimens reduced triglycerides, but only in the group with higher dietary saturated fat did HDL increase.
The VHFLC diet also led to significantly greater reductions of other heart disease risk factors related to body composition, including waist circumference, abdominal fat mass, visceral fat, and total body weight.
Dietary saturated fat intake in the study accounted for 34 per cent of energy in the VHFLC diet – which is 21 per cent more saturated fat than what consumes the average UK adult.
These findings, published in the American Journal of Clinical Nutrition, do not support maintaining the recommended upper limit on saturated fat at 10 per cent of calories in vigour for the UK.
Recommended intakes for saturated fat are routinely not revised upwards because what is conventionally considered to be healthy heart diets (Mediterranean or Ornish) are within these upper limits.
As a result, dietary guidelines encourage people to replace saturated fats with carbohydrates or omega-6 polyunsaturated fat. Replacement of saturated fat by carbohydrates, particularly refined carbohydrates and added sugars, has been shown to increase levels of triglycerides and reduce HDL cholesterol, thereby increasing cardiovascular risks.
Irrational fear of saturated fat in the context of the diet-heart hypothesis is the reason many are not embracing very effective balanced low carb, high fat diets for the treatment of type 2 diabetes and obesity today, and it needs to change.

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