Health: Why Are My Thighs Still Fat?

You try to eat right, you try to be more active, but your legs aren’t fitting into your jeans now any better than they were last month. What’s the cause?

The length of your legs is a matter of genetics. Studies show that, in general, the average 18- to 45-year-old woman’s legs (determined by crotch height) make up about 45 percent of her total height versus 44 percent for the average man in the same age group.

Your leg muscles are another story – how they look depends both on your genes and your daily habits. We all have the same main leg muscles: the quadriceps, the hamstrings, and the adductors make up the thighs, the below-the-knee tibialis anteriors make up the shin muscles, and gastrocnemius and soleus muscles make up the calves.

But there’s a wide range of sizes and muscle makeup among people that even experts debate. According to Daniel Lieberman, PhD, professor of human evolutionary biology at Harvard University, muscle fibers in humans evolved so that most of us have legs with a majority of slow-twitch fibers, which give us our staying power during long runs. “We’re built more for endurance, whereas chimps have more fast-twitch fibers,” he explains.

The Problem?

Since puberty, women’s hormones signal for fat cells to be stored around your butt and thighs, ultimately to help serve as reserve energy for pregnancy and breastfeeding. “Women tend to gain fat in very specific body parts, mostly those from the waist to the knee,” explains Andrew Da Lio, MD, professor and chief of plastic and reconstructive surgery at University of California, Los Angeles. The most common of those parts is the outer thigh, he says, even if your body type isn’t specifically a pear shape.

The problem is that many women are often so afraid of getting bulky thighs and calves that they neglect to strength-train their legs. Actually, bulky legs are mainly due to fat. With lack of activity and poor eating habits, we start accumulating fat, and it affects the function and strength of muscle.”

There are two levels of fat in the legs, Dr. Da Lio explains: a superficial layer and a deeper one. The superficial layer is where we find the puckered tufted-mattress look we call cellulite when extra fat bulges out between the tissues that connect skin to underlying muscle. The good news is that this deeper layer is also typically the first layer of fat to shrink when we exercise.

Are You Sitting Too Much?

“Sitting is the new smoking; it’s just as insidious,” says Marc Hamilton, PhD, a physiology professor at the Pennington Biomedical Research Center in Baton Rouge, Louisiana. Hamilton is making a point about how so many Americans are letting their leg muscles — and therefore their bodies — turn to mush. “You’ve seen the flat line on an EKG, when all the doctors rush in? That’s what’s happening to your leg muscles when you’re sitting.”

Can Standing At Work More Make a Difference?

“Standing while talking on the phone or filing isn’t exercise by anybody’s standard,” Hamilton says, “yet, compared with sitting, it increases your metabolic rate a bit.” According to a widely accepted compendium of physical activity, doing “light office work” while sitting burns 96 calories an hour for an average 140-pound woman as opposed to 147 calories while standing. Besides, Hamilton adds, “when we’re sitting for extended periods, hundreds of ‘bad’ genes are turned on, including ones that stimulate muscle atrophy.”

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