The Hidden Reason You're Gaining Weight

You're eating right and working out, yet your pants keep getting tighter. Don't blame your dry cleaner or your fork or your ab crunches. Check your thyroid. When it's sluggish -- as it is in millions of North Americans -- you can pack on the pounds and inches despite your healthiest efforts.

Plenty of things go awry when your thyroid is loafing, but they can be so subtle that most people blow them off until extra weight sounds the alarm. Symptoms include dry skin, joint or muscle aches, cold intolerance, fatigue, shifts in sexual drive, menstrual changes in women, and even depression -- all stuff that's easy to chalk up to being overtired or overstressed or to just feeling guilty about gaining weight. But more sleep or more willpower won't help you. What will? Getting your thyroid tested.

Women over 40 are at highest risk; after 50, up to 10% struggle with sluggish thyroids, though they often don't know it. And it gets more common: By age 60, 15% to 20% of women and 5% of men have abnormally slow thyroids. While the cause isn't clear, there's new evidence that gaining weight itself seems to affect thyroid function -- which, of course, makes it easier to gain even more weight.

Basically, your thyroid, a tiny gland at the base of your neck, produces hormones that control your metabolism -- which means your little thyroid can affect the function of everything from your heart and lungs to your emotional well-being. If your thyroid slows down, sooner or later your belt size will go up, because you're burning fewer calories.

Mention any suspicious symptoms to your doctor. And even if you feel fine, get your thyroid checked at age 35, and every other year after that. This involves two simple blood tests: TSH and free T3/T4. Why two? To get the whole picture. Your hypothalamus (a brain gland) pumps out a substance that stimulates the pituitary gland to release TSH (thyroid stimulating hormone, as long as we're getting technical). TSH tells your thyroid to pump out T4, which is converted to T3. If you have too little T3, your brain tries to increase TSH, which drives your thyroid gland -- like a jockey on a horse -- to go faster and produce more T4. So if you have normal T4 but elevated TSH, it could mean your thyroid system needs hormonal help. (You see why medical school is necessary).

Sounds like the next step should be simple (just give me some T4, doc!), but you need combo T3/T4 pills to affect your TSH -- and your waist and weight.

Actually, it's even more complicated than that -- that's why general physicians like Dr. Mike call in specialists (in this case, endocrinologists). It's not always clear whether we should treat the numbers or treat the symptoms. And the numbers themselves are wild. The so-called normal range for many levels is defined as the middle 95% (yes, 95!) of people with those levels; the top 2.5% are considered high, and the bottom 2.5 percent are considered low. Unfortunately, that's like saying that if normal is a size 6 to 11 in shoes, then a 6 shoe will be okay for you, even if you wear a size 4. Not a good fit, but you'd still be wearing a "normal" size.

That's why docs can choose to treat the symptoms -- in other words, get you a shoe that's comfortable -- as long as the treatment doesn't cause very abnormal levels on blood tests. Your doctor needs to work with you, possibly backing off now and then to see if you can be symptom-free with less thyroid hormone. Thyroid disease is tricky, so you need to consider your doctor a partner in your healthcare, and you need to be the active other half of that partnership.