CBS News chief medical correspondent Dr. Jon LaPook and CBS News contributor Dr. Holly Phillips joined "CBS This Morning: Saturday" to discuss the major medical stories of the week.
A major new study has drawn a clear link between testosterone supplements and heart attacks.
The supplements are taken by millions of American men but this study - the largest to date - raises serious questions.
An analysis by UCLA of insurance claims from more than 55,000 men looked at the rate of heart attacks within 90 days of starting testosterone.
In men 65 and older, the risk more than doubled. In men younger than 65 with a history of heart disease, the risk almost tripled.
Testosterone treatment is only FDA-approved for conditions linked with so-called low "T" - documented low testosterone levels. But many men without low "T" are being treated for a variety of symptoms, such as fatigue and diminished libido.
A study earlier this month found 43 percent of men receiving the hormone had a normal level.
Cardiologist Dr. Steven Nissen, of the Cleveland Clinic, told CBS News, "We don't know much about this therapy. What's going on is a giant experiment with American men's health at stake because we don't have the long-term data on the safety of these products."
Annual prescriptions for testosterone more than doubled in just four years to 430 million, thanks in part to advertisements on TV.
Nissen said, "Once it appears on television, with seductive ads that make men think it's a fountain of youth, you're going to see a lot of off-label usage."
LaPook said on "CTM: Saturday" that this new study is so important because of where it sits in the arc of researching testosterone. He said, "This is now the biggest study to date, and it shows that not only is there an increased risk in men who are over 65 but there's a new group - under 65-year-old men who have had a previous history of heart disease. Now, this is not the gold standard test. It doesn't show cause and effect, but thinking about how this use has exploded over the last few years, it's really a reason to be concerned."
Why? LaPook explained, "One thing is that testosterone use might increase clotting of the blood vessels that supply the heart and therefore they could cause a heart attack."
Also this week, a new study shows that the road to obesity starts before age 5. Research in the New England Journal of Medicine finds kids who are overweight in kindergarten are four times as likely to be obese in the eighth grade.
Phillips said, "It's basically showing us that the dye is cast so incredibly early in our lifetime for obesity risk. … There really isn't such a thing as baby fat. It all matters."
Phillips said the body mass index can be calculated as young as age 2, looking at height versus weight. If a child is over the 85th percentile, the child is overweight, and if the child is over the 95th percentile, the child is obese.
She added, "These things really matter, even as young as age 2."
The impact of being overweight or obese on kids, Phillips said, is even worse than on adults because they'll have symptoms - perhaps for diabetes, heart disease, high blood pressure, asthma, and sleep problems - for a longer time. She said, "We're actually being able to predict that they might even have a shortened lifespan if they remain obese for their entire life."For Dr. Jon LaPook and Dr. Holly Phillips' full roundup on this week's medical stories, watch the video in the player above.