The data, published in the American Journal of Clinical Nutrition, come from a randomised diet intervention study (known as the FATFUNC study) which tested how different diets containing high levels of either carbohydrate or fats influenced fat storage and markers of metabolic syndrome in men with abdominal obesity.
Led by first author PhD candidate Vivian Veum from the KG Jebsen centre for diabetes research at the University of Bergen, the team reported "strikingly similar" health effects of the two diets, and that the three month interventions “did not differentially influence visceral fat and metabolic syndrome.”
“Our data do not support the idea that dietary fat per se promotes ectopic adiposity and cardiometabolic syndrome in humans,” the Norwegian researchers said.
"The very high intake of total and saturated fat did not increase the calculated risk of cardiovascular diseases," commented study co-author Professor Ottar Nygård.
"Participants on the very-high-fat diet also had substantial improvements in several important cardiometabolic risk factors, such as ectopic fat storage, blood pressure, blood lipids (triglycerides), insulin and blood sugar."
Veum and colleagues randomly assigned 46 middle-aged men (aged between 30 and 50 years) with body mass index above 29 kg/m2 and waist circumference above 98 cm to either a very high–fat, low-carbohydrate (VHFLC; 73% of energy fat and 10% of energy carbohydrate) or low-fat, high-carbohydrate (LFHC; 30% of energy fat and 53% of energy carbohydrate) diet for 12 weeks.
“The diets were equal in energy (8750 kJ/d), protein (17% of energy), and food profile, emphasizing low-processed, lower-glycaemic foods,” said the authors.
"We here looked at effects of total and saturated fat in the context of a healthy diet rich in fresh, lowly processed and nutritious foods, including high amounts of vegetables and rice instead of flour-based products," added Veum, noting that the fat sources were also minimally processed and “mainly butter, cream and cold-pressed oils."
The team analysed adiposity and metabolic syndrome markers through detailed measures of fat mass in the abdominal region, liver and heart, in addition to a number of key key risk factors for cardiovascular disease like blood pressure and cholesterol.
According to the team, both the LFHC and VHFLC diets similarly reduced waist circumference (11–13 cm), abdominal subcutaneous fat mass (1650–1850 cm3), visceral fat mass (1350–1650 cm3), and total body weight (11–12 kg).
“Both groups improved dyslipidaemia, with reduced circulating triglycerides, but showed differential responses in total and low-density lipoprotein cholesterol (decreased in LFHC group only), and high-density lipoprotein cholesterol (increased in VHFLC group only),” the Norwegian team said.
Indeed, they noted that although saturated fat has been thought to promote cardiovascular diseases by raising the ‘bad’ LDL cholesterol levels, the current FATFUNC findings found no significant increase in LDL cholesterol.
Rather, they saw that ‘good’ cholesterol increased only on the very-high-fat diet.
"These results indicate that most healthy people probably tolerate a high intake of saturated fat well, as long as the fat quality is good and total energy intake is not too high. It may even be healthy," Professor Nygård added.
The findings follow a recent joint study from the Harvard School of Public Health and Unilever which found an association between higher intakes of specific saturated fats (C12-C18) and the risk of coronary heart disease.
However, reactions to the study from Professor Tom Sanders of King’s College London and Dr Nita Forouhi from the University of Cambridge noted that it failed to investigate saturated fats found in dairy – which have previously been linked to reductions in heart disease risk despite being classified as a saturated fat.
Given that the new Norwegian study focused on minimally processed saturated fats including dairy, the two results may not be so conflicting after all.
Source: The American Journal of Clinical Nutrition
Published online ahead of print, doi: 10.3945/ajcn.115.123463
“Visceral adiposity and metabolic syndrome after very high–fat and low-fat isocaloric diets: a randomized controlled trial”
Authors: Vivian L Veum, et al