Studies giving fat the all clear 'are misleading', say scientists

A study published in March that suggested eating a lot of fat may not be bad for you was misleading, nutrition scientists have concluded.

The findings generated a welter of headlines earlier in the year, but despite the claims it now appears that saturated fats in foods including cakes, butter, processed meat and hard cheese are bad for your heart after all.

The reports were based on the findings of Dr Rajiv Chowdhury of Cambridge University, whose team concluded that polyunsaturated fats in olive oils and fish were not necessarily more healthy for us. Chowdhury's research "overturned the assumptions of decades", The Guardian notes. But was his data reliable?

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Christine Williams, professor of human nutrition at Reading University, says that research into consumption habits, such as Chowdhury's, is "notoriously problematic" because people tend to under-report the food they have consumed if they know that food is bad for them. "About 60 per cent [of people] when asked what they eat systematically under-report by 20-30 per cent their energy [intake]," she said. "Overweight people are more likely to do so than underweight people."

Tom Sanders, professor emeritus of nutrition and dietetics at King's College London agreed: "People lie about what they eat," he said. "We get served too big portions in pubs and restaurants and then we go and get a coffee and are asked if we want a muffin with that. You go and buy a newspaper and are asked if you want a 100g bar of chocolate and there are high-sugar, high-fat snacks on the way to the counter. A muffin at breakfast can be 600 calories and then you add the latte and it can be 1,000 calories, half your daily recommended intake in one go."

Studies can also arrive at misleading conclusion if they ask people to report on their diets only at one point, such as a particular day or week's worth of eating, and then project forward from that information for years to come.

According to Andy Salter, head of nutritional sciences at the University of Nottingham, almost all studies into the effects of fats, including numerous experiments that have been conducted on both humans and animals, indicate that diets high in saturated fats lead to large amounts of "bad" low-density lipoprotein (LDL) cholesterol in the blood. This cholesterol can build up on the artery walls, leading to disease of the arteries, as well as heart attacks and stroke.