Information adapted from the book The Thyroid Diet: Manage Your Metabolism for Lasting Weight Loss
Many hypothyroid patients struggle with an inability to lose weight. At first, if you'd gained weight before your thyroid problem is diagnosed, you were probably told you'd be able to lose it more easily -- or perhaps you were even told you'd lose all the extra weight -- once you started on your thyroid hormone replacement.
So you take your thyroid hormone, and the weight doesn't come off.
Later, despite "normal" TSH levels, and lower-calorie, low-fat diets and exercise, you find yourself still gaining, or not losing weight. You may also have high cholesterol levels. The doctor then tells you that your weight problem doesn't have anything to do with your thyroid.
Some of this site's visitors have reported to me that they were on a 900-calorie a day diet, walking 3 miles a day, and not losing weight, and the doctor says, "well, you just must be eating too much."
What thyroid patients need to know more about are three factors that are likely at work for many of us with a difficulty losing weight -- a changed metabolic "set point," changes in brain chemistry due to illness and stress, and insulin resistance.
Metabolic Set Point
According to Dr. Lou Aronne, author of the best-selling Weigh Less Live Longer, when you begin to take in too many calories, you have a small weight gain. Then, in order to maintain your set point weight, "your metabolism speeds up to process the excess calories, your appetite decreases, and some of the newly gained weight drops off." He calls this metabolic resistance.
Dr. Aronne believes that every person's body has what is called a weight "set point." Just like your body works to maintain a temperature "set point" of 98.6, it also appears to work toward maintaining a particular weight "set point."
His theory is that in people with a chronic weight problem, the body puts up only modest metabolic resistance to weight gain. If you continue to take in more calories than you burn, the metabolic resistance loses strength, and your body then establishes a new, higher weight set point.
What this means is, if several years ago, as a woman at 5'7" and 160 pounds you needed 2500 calories a day to maintain your weight, and now, after a diagnosis of hypothyroidism and a steady weight gain, at 210 pounds, you need 2800 calories to maintain your weight, if you dropped your calories back to 2500, would you lose the extra 50 pounds? No, as you reduce your calories and lose weight, your metabolic rate slows down, and according to Dr. Aronne, you'd probably only drop to around 197 pounds, although you'd be consuming the same number of calories as another woman of the same height who's stayed steady at 160 pounds.
This is probably the mysterious factor at play when we see someone who apparently eats even more than we do, but maintains a lower weight level, or conversely, the person who swears they don't eat that much, but gains weight, or stays heavier.
Dr. Aronne believes you can't completely eliminate the metabolic resistance, but a slow steady approach to dieting helps to minimize it. Also, a key way to increase metabolism is through exercise.
Changes in Brain Chemistry
Hunger is intricately tied to your brain chemistry. According to Dr. Aronne, your hypothalamus senses you need energy, and issues the brain neurotransmitter neuropeptide Y (NPY) with the message "eat carbohydrates." The surge of NPY is what you experience as "hunger," Once the hypothalamus senses you've eaten enough carbohydrates, it releases serotonin to tell the body, "enough carbohydrates."
But this system can be dramatically altered by several factors, all of which can be present in chronic thyroid disease:
- Your metabolism is too slow for the appetite level set by your brain. Thyroid disease slows down the metabolism. What your brain perceives as appropriate food intake levels can then exceed your body's metabolism, creating weight gain.
- Your body is under stress, which interferes with the neurotransmitter functions, and is known to reduce the release of serotonin. In fact, part of the success of the recently recalled diet drugs fen-phen was the fact that they increase serotonin and create a "feeling of fullness."