Nutrition research can make for attention-grabbing headlines. Here, we cut through the hype – and clarify the real take-home message – for you.
Bring back the saturated fat?
A new study looking at the merits of a low-carbohydrate, high-fat diet, compared to a low-fat diet, has attracted attention for what it may be saying about the health effects of saturated fat. The study, published in the American Journal Clinical of Nutrition, looked at how a low-carb and a low-fat diet fared for their benefits on metabolic health on 46 overweight men. This wasn’t just another diet comparison diet. The novel aspect was that both diets included the same types of minimally processed foods; only the macronutrient amounts of fat, saturated fat and carbohydrate varied.
The hype: How the media conveyed the news
For a study with so many facets, some of the media attention just focussed on saturated fat and declared its health merits. Saturated fat could be good for you (EurekaAlert!) and Saturated fat could be good for you, study suggests (Science Daily).
The low-carbohydrate group ate almost 3-times the amount of saturated fat as the low-fat group courtesy of their much higher overall fat intake. But context is king and the high saturated fat intake was part of a healthy diet rich in fresh, minimally processed nutritious foods, including high amounts of vegetables and very low in added sugar.
Much of the media focus was on the higher HDL and no increase in LDL in the low-carbohydrate group. But little focus was given to the fall in LDL and improvement in blood glucose that was seen only in the low-fat group. One can spend all day arguing a case for any diet with so much biochemistry on hand, but the truth is that the results of one study, done for 3 months, can tell us little about life-long disease risk from following a constructed diet. To isolate the effect of saturated fat alone, a comparison high-fat diet that was rich in unsaturated fats would be needed.
But are the results from the study surprising? The research is a great example of focussing on overall diet quality first, rather than nutrients. Looking at the forest, rather than trees, so to speak. And when this is done, differences between contrasting dietary approaches begin to narrow. The greatest predictor of weight loss and improved metabolic health is adhering to the diet approach a person is following, not so much the type of diet type they are on. Of course, the long-term failure of most of these diets is a story for another time.
But can we really conclude from this study saturated fat is healthy for us? The answer is ‘no’, at least not when weight loss is occurring. And the reason for this is that we eat foods, not nutrients. Our diet is a complex mixture of nutrients and putting a spotlight just on a single nutrient misses the bigger picture. In an excellent commentary by Rosemary Stanton on The Conversation, she showcased how classifying saturated fat as ‘good’ or ‘bad’ is a red herring when you consider that the same quantity of saturated fat is found in 35 grams of cheese, 35 grams of white chocolate, 70 grams of potato crisps, 90 grams of roasted cashews, a small rump steak, a tablespoon of lard, 50 grams of polyunsaturated margarine and a small custard tart. All, very different types of foods!
The truth: The research findings
In line with so much prior research, adhering to any form of diet (at least in the short-term timeframe of 3 months) has benefits on body weight and metabolic health. Both groups saw similar changes in body weight and waist circumference. Dyslipidaemia improved in both groups, although the low-fat group was superior for reducing total and LDL-cholesterol and fasting glucose while the low-carb group was superior for increasing HDL-cholesterol.
The reality: Putting the findings into practice
Even in controlled clinical trials, there can be tremendous individual variation in responses to different dietary approaches, making it difficult to declare any dietary approach ‘the winner’ in head-to-head comparisons. This new study shows that different approaches can work for improving metabolic health when the focus is about broad nutrition recommendations that are about eating more fruits and vegetables and minimally processed foods. Then, tailor this advice to sustainable dietary changes for your client or patient.
Tim is an Advanced Accredited Practising Dietitian, and career nutrition research scientist and media communicator. Connect with him at www.thinkingnutrition.com.au.