London, August 14: Feeling inactive and slow? Blame it on your high-fat diet.
According to a new study, Oxford University experts reaffirm the well-known notion of high-fat diet leading to sluggishness.
The revelations came into light when rats fed on a high-fat diet showed a stark reduction in their physical endurance and a decline in their cognitive ability merely after nine days.
“We found that rats, when switched to a high-fat diet from their standard low-fat feed, showed a surprisingly quick reduction in their physical performance,” says Dr. Andrew Murray, who led the work at Oxford University.
“After just nine days, they were only able to run 50 per cent as far on a treadmill as those that remained on the low-fat feed”, he says.
There are possible implications not only for those eating lots of high-fat foods, but also athletes looking for the optimal diet for training and also the patients with metabolic disorders, FASEB Journal added.
During the study, the physical endurance of all 42 rats was measured after they were fed a low fat content of 7.5 per cent and their short-term or ‘working’ memory was measured in a maze task.
Half of the rats were then switched to a high-fat diet where 55 per cent of the calories came from fat.
“With the standard feed, 7.5 per cent of the calories come from fat. That’s a pretty low-fat diet, much like humans eating nothing but muesli. The high-fat diet, in which 55 per cent of the calories came from fat, sounds high but it’s actually not extraordinarily high by human standards. A junk food diet would come close to that”, Dr. Murray says.
“Some high-fat, low-carb diets for weight loss can even have fat contents as high as 60 per cent. However, it’s not clear how many direct conclusions can be drawn from our work for these diets, as the high-fat diet we used was not particularly low in carbs,” he adds.
On the fifth day of the high-fat diet (the first day back on the treadmill), the rats were already running 30 per cent less far than those remaining on the low-fat diet. By the ninth day, the last of the experiment, they were running 50 per cent less far.
Their cognitive abilities were also being affected by their diet as the number of correct decisions by rats on high-fat diet dropped from over six to an average of 5 to 5.5.
High-fat diets, such as those that are prevalent in Western countries, have widely been known to be harmful in the long term, leading to problems like obesity, diabetes, heart failure and a decline in cognitive ability as well.
The researchers also investigated what metabolic changes the high-fat diet was inducing in the rats. They found increased levels of a specific protein called the ‘uncoupling protein’ in the muscle and heart cells of rats on the high-fat diet.
This protein ‘uncouples’ the process of burning food stuffs for energy in the cells, reducing the efficiency of the heart and muscles. This could at least partly explain the reduction in treadmill running seen in the rats.
The rats that were fed a high fat diet and had to run on the treadmill also had a significantly bigger heart after nine days, suggesting the heart had to increase in size to pump more blood around the body and get more oxygen to the muscles.
“In little more than a week, a change in diet appears to have made the rats’ hearts much less efficient, Prof Jeremy Pearson of the British heart Foundation has said.
“We look forward to the results of the equivalent studies in human volunteers, which should tell us more about the short-term effects of high-fat foods on our hearts. We already know that to protect our heart health in the long-term, we should cut down on foods high in saturated fat,” he added.
Physical endurance depends on the amount of oxygen that can be supplied to our muscles and how efficiently our muscles release energy by burning up the fuel we get from the food we take.
In particular, using fat as a fuel is less efficient than using glucose from carbohydrates, but the metabolic changes induced by different diets are complex and it has been controversial whether high-fat feeding for a short time would increase or decrease physical performance.
The Oxford team is now set out to investigate whether rats fed a high-fat diet for just a few days showed any change in their physical and cognitive abilities.
–PTI