MedicalResearch.com Interview with:
Dr. Ulf Risérus
Associate Professor in Clinical Nutrition
Department of Public Health and Caring Sciences
Clinical Nutrition and Metabolism
Faculty of Medicine, Uppsala university
MedicalResearch.com: What are the main findings of the study?
Dr. Risérus: It has previously been shown in animal studies that overfeeding polyunsaturated fat causes less fat accumulation than saturated fats, but this study is the first to suggest that this could be true also in humans. Overeating saturated fats caused significantly more accumulation of fat in the liver and intra-abdominally, as compared with overeating polyunsaturated fats from. This study suggests it does matter where the excess calories come from when we gain weight. If a high-caloric diet contains large amounts of saturated fats it seems to switch on some genes that may promote abdominal fat storage and insulin resistance, and thereby result in a more unfavorable fat storage. In contrast, such effects were not seen if the diet was lower in saturated fats but higher in polyunsaturated fats from non-tropical vegetable oils. This study also suggests a novel contributing factor regarding the tendency of some individuals to accumulate fat in the liver and abdomen, i.e. in some people excessive amounts of saturated fat in combination with sugars might induce more fat in their livers and a propensity towards abdominal visceral fat accumulation.
MedicalResearch.com: Were any of the findings unexpected?
Dr. Risérus: The results regarding the increased muscle mass following consumption of polyunsaturated fat was unexpected but highly interesting, and thus a finding we will follow-up in future studies. In more simple words overeating saturated fat may build more fat but less muscle, whereas the opposite was found when instead overeating polyunsaturated fats. We are currently investigating this in additional studies and are trying to understand the mechanisms behind this finding.
MedicalResearch.com: What should clinicians and patients take away from your report?
Dr. Risérus: It is previously known that replacing saturated fat with polyunsaturated fat lowers LDL cholesterol in the blood , but the current data also suggests that irrespectively of the calorie content of the diet, individuals could benefit from having a good balance between polyunsaturated fat and saturated fats in the diet to avoid exaggerated liver and visceral fat accumulation, which may also influence the risk of developing obesity-related diseases in the long-term. These new findings also support international and US dietary recommendations, which, among other things, recommend replacing some saturated fat from red meats, butter, and palm oil, for example, with unsaturated fats from plant oils, nuts and fatty fish.
As there is a strong, and potentially causal link, between visceral fat accumulation and fatty liver (including non-alcoholic fatty liver disease, NAFLD) on the one hand and type 2 diabetes and cardiovascular disease on the other, the present results are of high interest. If confirmed, the results may be clinically important for better and early prevention of NAFLD, visceral obesity and potentially type 2 diabetes. These results however needs further investigation before we know the true clinical implications of dietary fat modification in preventing NAFLD and metabolic disorders such as type 2 diabetes.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Dr. Risérus: The next step is now to find out in greater detail what happens in the body when we eat the respective fats and to study what the effects are in overweight individuals with elevated risk of type-2 diabetes.