Eating too much butter, cakes, cookies and junk food for just three weeks can dangerously increase internal fat and cholesterol – even if you stay slim.
According to an Oxford Uni study, 24 people followed a diet high in saturated or polyunsaturated fats for up to 24 days.
Those who ate more saturated fat had a 20 percent increase in fat around the liver and a 10 percent increase in blood cholesterol, even though they did not gain weight.
Study leader Nikola Srnic, a PhD student, said: “It’s interesting how you can see such a change so quickly, in three weeks.
“Our health is a very complex picture, and while looking at the numbers on the scale is one metric we’ve used for many years, there are other factors besides body weight that affect health.”
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People on a saturated fat diet were asked to increase their consumption of foods, including full-fat dairy products, pastries and cakes.
Those on the polyunsaturated fat diet ate more fatty fish such as mackerel and salmon, vegetable oils, nuts and seeds.
The latter group’s total blood cholesterol and “bad” cholesterol levels dropped by about 10 percent, and their heart muscle energy stores increased.
Srnic said the findings highlighted the protective role of certain fats and the dangers of other fats even without weight gain.
He added: “It’s the type of fat, as well as the amount of fat, that’s important. Losing weight is the best way to reduce your risk of metabolic disease.
“But what we’re seeing here is that you can still get some beneficial effects, although not on the same scale, if you just change the type of fat you’re consuming. If you’re not losing weight, you shouldn’t lose hope.”
The researchers also studied cardiomyocytes grown in conditions enriched for each type of fat.
Cells exposed to polyunsaturated fats became more active in taking up fat and breaking it down into energy, which may explain why consuming these foods can help lower blood fat levels.
Professor James Leiper, deputy medical director of the British Heart Foundation, said: “Saturated fat has long been known to cause a much higher risk of cardiovascular disease.
“This study adds to that consensus and gives us evidence that saturated fat can quietly start to pose a risk to heart health very quickly without causing changes in a person’s weight.”
Clare Thornton-Wood, pediatric nutritionist at the British Dietetic Association, said: “This is a really interesting study that supports the already established evidence that saturated fat intake is associated with an increase in heart disease.”
The research was presented at the European Society of Cardiology’s annual conference in London this weekend.
