Yes, we all know, as we have heard it some umpteen times that a healthy diet is the key to an active and long life, shielding us for various ailments. But ‘healthy’ doesn’t always match up to the delight of our taste buds. Sure, many restaurants and home chefs today are finding interesting ways to spruce up healthy food, however, when the inevitable cravings set in we just can’t think beyond greasy, life threatening yet extremely delicious ‘junk’ foods. How harmful could a little indulgence be?
The ugly truth is that these high-fat foods not only make you hit the roof on the calorie chart, leading to obesity and heart diseases in the long run, but bring much more harm to the normal functions of the body without you even knowing of it.
A recent study done by the Medical College of Georgia in the US states that a high-fat diet may not only make us obese, but could also cause cognitive impairment by prompting immune cells in the brain to consume the connections between neurons. Going back on a low-fat diet for just two months could help, as was found during experimentations on mice, which reversed this trend of shrinking cognitive ability as the weight began to normalise, said corresponding author of the study, Alexis M Stranahan.
"Microglia eating synapses is contributing to synapse loss and cognitive impairment in obesity," said Stranahan. The study provides some of the first evidence of why fat is bad for the brain. Too much fat in the body produces chronic inflammation, which stimulates microglia to have an autoimmune response.
Microglia, like macrophages in the body, are known for their ability to ingest trash and infectious agents in the brain, and their highly acidic interior gets rids of it, which helps support the function and health of neurons. However, it was found that as mice get obese, their microglia seem focused on overeating.
"Normally in the brain, microglia are constantly moving around. What happens in obesity is they stop moving," Stranahan said. "They draw in all their processes; they basically just sit there and start eating synapses. When microglia start eating synapses, the mice don't learn as effectively," said Stranahan.
The study looked at male mice - one group ate a diet in which about 10 per cent of the calories came from saturated fat, and another consumed chow that was 60 per cent fat. At four, eight and 12 weeks, the scientists took a series of metabolic measures, such as weight, food intake, insulin and serum glucose levels. They also measured in the hippocampus, the centre of learning and memory, levels of synaptic markers, proteins found at synapses that correlate with the number of synapses. They measured levels of inflammatory cytokines, which microglia produce when they start getting activated.
By 12 weeks the fat-eating mice were obese, had elevated cytokine levels and a reduction in the markers for synapse number and function. At that point, the research team switched half the mice on the high-fat diet to the low-fat regimen. It took about two months for their weight to return to normal, although their overall fat pad remained larger than their peers who had never gained weight.
As with most people, the mice that remained on the low-fat diet slowly accumulated a little weight as they aged. Meanwhile, the group that stayed on the high-fat diet kept getting fatter, more inflamed and losing synapses.
Their microglia's little processes, or protrusions, which normally help monitor synaptic function and help these cells move, continued to wither. The study was published in the journal Brain, Behaviour and Immunity.