Dieting - does it really lead to weight loss?
Hypothyroidism, reduced thyroid hormone levels, is associated with slow metabolism and weight gain (1). For many with hypothyroidism, weight control is one of their biggest frustrations. When someone needs to lose weight, the most common solution given is a reduced calorie diet. But for many, these diets don’t work. People either don’t lose weight, or they lose weight but quickly gain it back, often with a few additional pounds (2, 3). What many people don’t know is that severe or chronic dieting can reduce the active thyroid hormone, Triiodothyronine (T3), causing the metabolism to slow and weight loss to become more difficult.
A little background – What are our thyroid hormones? You may already know that thyroid hormone is the ‘master hormone’ when it comes to regulating your metabolism (1, 4). Your metabolism involves a series of processes that break down food and convert it into the energy your body needs to run. It also determines how quickly (or slowly) your body uses calories.
Thyroid Stimulating Hormone (TSH), created by the pituitary gland, tells the thyroid (the butterfly-shaped gland located just under your larynx in your neck) to make thyroxine. Thyroxine, or T4, is an inactive thyroid hormone that must be converted before it has an effect on the body. T4 can be converted to triiodothyronine (T3), the active hormone that regulates your metabolism.
So, how does dieting and calorie restriction throw things off? When you drop your calorie intake too low, less T4 may be converted to T3. Instead, more is made into something called reverse T3 (5, 6). The problem with reverse T3 is it isn’t active. What it does do is bind to the same receptors that T3 does and makes it difficult for T3 to bind. With reverse T3 keeping active T3 out of the picture, you may burn less fat and carbohydrates and your metabolism, along with everything else, slows down. Or, explained more simply, you may have difficulty losing weight and keeping weight off.
But that’s not the whole story ... Your body considers eating too little and not getting enough nutrients to be a serious threat. Your body doesn’t know there’s plenty of food in the kitchen and you’re choosing not to eat. Instead, your body is gearing up for a famine. Cortisol, a stress hormone produced by our adrenal glands, is needed in large amounts during this timeframe to keep your blood sugar as steady as possible. So, while this doesn’t really seem like an emergency to you, it does to your body, and you begin pumping out high levels of cortisol (7).
Not only does your body respond to this perceived famine, but it also responds to the sense of deprivation and restriction. You may not even be aware of this stressor because you’re not paying attention to the negative emotion that is coming from your restriction and the constant monitoring, worrying, and calculating that takes place when you overly control your eating habits — but your brain definitely notices and this psychological stress also increases cortisol (7).
When your body relies on cortisol too much, there can be a tendency to gain fat particularly around the midsection. This is because there are more cortisol receptors in belly fat. So, your body is going to think you need as many receptors (and fat cells!) as possible to keep up with the demand.
What now? In a nutshell, extreme dieting and calorie restriction in an effort to lose weight can backfire by reducing thyroid function, slowing down your metabolism and increasing stress levels.
My tips to improve your health now are: 1. Stop dieting – diets do not work! 2. Eat a balanced diet based on whole, real, nutrient-dense, properly prepared foods — and lot of them! 3. Take the time to relax and unwind. Even if you don’t restrict your calorie intake, but still lead a stressful life, cortisol will still impact your body.
If this is something you think you may be dealing with, let’s talk. I have helped many people (including myself!) address thyroid issues, balance their blood sugar and cortisol levels with diet and lifestyle changes.
1. Mullur, R., Liu, Y.Y. & Brent, G.A. (2014). ‘Thyroid hormone regulation of metabolism’. Physiological Review, 94(2): 355 - 82. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4044302/
2. Kraschnewski, J.L., Boan, J., Esposito, J., Sherwood, N.E., Lehman, E.B., Kephart, D.K. & Sciamanna, C.N. (2010). ‘Long-term weight loss maintenance in the United States’. International Journal of Obesity, 34: 1644 – 1654. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3671378/
3. Turk, M.W., Yang, K., Hravnak, M., Sereika, S.M., Ewing, L.J. & Burke, L.E. (2009). ‘Randomized clinical trials of weight loss maintenance: a review’. Journal of Cardiovascular Nursing, 24: 58 – 80. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2676575/
4. Brent, G.A. (2012). ‘Mechanisms of thyroid hormone action’. Journal of Clinical Investigation, 122: 3035 – 3043. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3433956/
5. Rosenbaum, M., Hirsch, J., Murphy, E. & Leibel, R. (2000). ‘The effects of changes in body weight on carbohydrate metabolism, catecholamine excretion, and thyroid function’. American Journal of Clinical Nutrition, 71: 1421 – 1432. https://www.ncbi.nlm.nih.gov/pubmed/10837281
6. Spaulding, S.W. et al. (1976). ‘Effect of caloric restriction and dietary composition of serum T3 and reverse T3 in man’. Journal of Clinical Endocrinology & Metabolism, 42(1): 197 - 200. https://www.ncbi.nlm.nih.gov/pubmed/1249190
7. Tomiyama, J., Mann, T., Vinas, D., Hunger, J.M., DeJager, J. & Taylor, S.E. (2010). ‘Low Calorie Dieting Increases Cortisol’. Psychosomatic Medicine, 72(4): 357 – 364. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2895000/
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