Burt Reynolds shocked fans recently when the once-strapping sex symbol made a rare public appearance, looking gaunt, frail, and using a cane.

The 79-year-old Hollywood legend appears to be facing a common problem among the elderly, which is the sudden loss of muscle mass and body weight. The condition often leads to difficulty walking and performing routine tasks.

In Reynolds’ case, his thin appearance is a striking contrast to his public persona as a macho leading man. However, a top internist tells Newsmax Health, that frailty is not an inevitable fact of aging.

“Becoming thin and losing strength does happen, but I have patients in their 80s who look younger than some I have who are in their 50s,” says Michael Zimring, M.D., an internist at Mercy Medical Center in Baltimore, Md., who has not treated Reynolds. “It all depends on the way they live.”

It may seem unlikely that a man such as Reynolds – so fit in his younger years that he played fullback for the Florida State football team – would end up so frail. But a string of serious health problems may have contributed to his weight loss.

Back in the 1980s, when filming the movie City Heat, he was struck in the face with a metal chair, which broke his jaw and left him with a painful condition called temporo-mandibular joint dysfunction, or TMJ disorder.

Unable to eat, he lost 30 pounds from his 5-foot-11 frame. Reynolds also became addicted to painkillers, a habit that took him several years to break.

In 2009 he underwent back surgery and in 2010 he had a quintuple heart bypass. He reportedly had trouble eating following the heart operation, and again lost a large amount of weight, sparking rumors he had AIDS.

In recent years, he has made fewer public appearances.

The biggest factor in avoiding frailty in old age is to quit smoking, Dr. Zimring told Newsmax Health.

There are photos showing Reynolds smoking cigarettes and cigars when he was younger, although he appears to have quit at some point.

“I can tell by looking at somebody if they were a smoker or not,” said Dr. Zimring. “If they look frail, it’s likely they were a smoker.”

The reduced lung capacity caused by smoking, can lead to weight loss in the elderly, he said.

An unhealthy diet, inactivity, and substance abuse also take a toll in later years, leading to reduced muscle mass and loss of coordination.

“When you are young and strong, your body can tolerate smoking or an unhealthy diet, but when you get older, you can go downhill,” Dr. Zimring said.

But what can you do?

Many older people turn to quick fixes, such as protein powder, to add weight, but it doesn’t always work, he warns.

“Protein powders don’t do any good. The only thing they do is make the people who are selling them rich,” he said. “Vitamin B12 shots don’t do any good, either, unless there is a reason why you are medically deficient in that vitamin.”

Dr. Zimring says testosterone supplements, which have gained a huge following in recent years, are no panacea.

“Unless a man is clinically deficient in testosterone, and is suffering from muscle wasting, I do not think it’s necessary,” he said.

Testosterone supplementation also carries risks, he says.

The FDA recently changed the labeling on “low-T” drugs to warn of a possible risks from heart attack and stroke. And although testosterone supplementation has not been linked to prostate cancer, blocking the hormone is a treatment for the disease.

There are natural steps that both men and women can take to prevent frailty as they age, said Dr. Zimring.

“Right now, I am at a medical conference in Portsmith, Va., and there are people who may look a little mature, but they are not frail or weak. They are riding bikes, exercising and being active,” he said.

Here are Dr. Zimring’s tips to stay strong and active into old age:

Eat healthy. This means lots of fruits, vegetables, and whole grains. “You want to cut down on carbs. I have eggs for breakfast, and maybe a little bacon, but instead of hash browns, I substitute pineapple.”

Exercise daily. “If you sit around watching TV, you’ll go downhill. If you were active when you were young, and you stay active, you’ll be fine.”

Keep your mind active. “Keep working. Be involved. Once people retire, if they don’t keep their minds active, they get frail and die.”