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Women who tend to store fat around the thighs, hips and buttocks may enjoy additional protection against dementia and stroke, a study suggests.
Tests in mice indicated that subcutaneous fat, which lies under the skin and causes cellulite, protects against inflammation-related disorders, including heart disease.
They found that female mice with high levels of this type of fat had lower levels of inflammation than male rodents. But when the women underwent a procedure similar to liposuction, the researchers saw their levels of brain inflammation skyrocket.
The sex hormone estrogen promotes the accumulation of subcutaneous fat. It’s it has a direct impact on fat cell storage, and excess fat generates the sex hormone.
Female mice had higher deposits of subcutaneous fat, the type of fat under the skin, and showed less evidence of brain inflammation than male mice with higher deposits of fat around their organs.
Evidence is starting to mount that not all fat is created equal, and it’s where you store that fat that really counts. The most dangerous type of fat is known as visceral fat, a firm inner layer that forms between the organs inside the abdomen. It is usually the cause of a beer belly and contributes to an undesirable apple body shape, which is considered the physique with the highest risk of health problems. Subcutaneous fat, on the other hand, is the wobbly type of fat that sits just under the skin and causes cellulite to form.
Their findings may help explain why women are more prone to inflammation and autoimmune diseases, as well as stroke, than men.
While estrogen is strongly linked to fat storage in female bodies, the hormone does not appear to be the underlying cause of subcutaneous fat’s protective power.
The team of experts in Georgia did not discover a direct link between the removal of subcutaneous fat and fluctuating estrogen levels. Rather, the lead scientist pointed to clear chromosomal differences between the XX female and the XY male to explain the protection the females have.
Men are more likely to store body fat around their organs, known as visceral fat, which creates the dreaded “beer belly.”
This type of fat puts them at greater risk of inflammation-related problems than premenopausal women.
During menopause, the ovaries stop producing estrogen and the body begins to store more visceral fat similar to that of men.
To test the theory that female subcutaneous fat is protective, scientists at Augusta University in Georgia recorded increases in adipose tissue and levels of sex hormones and brain inflammation in both male and female mice.
The mice were fed high-fat diets for six months to record how and where the male and female mice stored more fat tissue on their bodies over time.
The mice then underwent a liposuction-like procedure to remove some subcutaneous fat.
The researchers, led by Dr. Alexis Stranahan, found that loss of subcutaneous fat increased brain inflammation in women without changing their estrogen levels.
They reasoned that the distinctive patterns of fat could be a key reason for the protection against inflammation that female mice enjoyed before menopause.
Inflammation in the women’s brains was much more like that of men, including elevated levels of the hallmark promoters of inflammation, such as the signaling protein TNF alpha in the brain.
Dr Stranahan said: “When we took subcutaneous fat out of the equation, suddenly women’s brains began to exhibit inflammation in the same way as male brains, with women gaining more visceral fat.”
His findings were published in Diabetes magazine.
Overweight female mice, like human females, tend to have more subcutaneous fat than visceral fat than males.
The loss of some subcutaneous fat caused the female mice to see spikes in brain inflammation similar to the brains of the male mice.
It was only after reaching menopause, the transition in females during which menstruation stops, that female mice that did not lose subcutaneous fat but ate a high-fat diet showed similar levels of brain inflammation to males.
The study focused on two parts of the brain to record inflammation, the hippocampus and the hypothalamus.
The hippocampus plays an important role in learning and memory, while the hypothalamus controls hormones and keeps the body in a state of balance known as homeostasis.
Loss of subcutaneous fat could have very different impacts on different parts of the brain, which should be investigated, according to Dr. Stranahan.