The following post is the 4th in a 5-part series about hormones and weight gain after age 40. Parts one, two and three can be read by clicking on the links below.
- Part 1: The biology of aging
- Part 2: Why nutrition matters even more now
- Part 3: Exercise for hormonal balance
Part 4: Weight gain and sleep
After hot flashes and night sweats, what are the two most common complaints of peri-menopausal women? (other than husbands who can’t seem to clean up the counter or put the toilet seats down after themselves…)
I’ll give you a hint; one tends to go up and the other, down.
Weight gain (especially around-the-belly poundage) and sleep (or lack thereof).
Did you answer correctly? And did you know that the two might be related?
Study after study of sleep duration and body mass index show an inverse relationship between the two; people that get less sleep also tend to be overweight.
When we eliminate the participants whose disordered sleeping is a consequence of being overweight (recall that correlation can’t, by itself be used to infer causation; check out my post on understanding the results of human health studies if you’re unclear on the concept), we find that moderate sleep deprivation disrupts a number of hormonal systems, several of which are involved in appetite, carbohydrate metabolism and fat storage.
- Cortisol. Production of cortisol varies rhythmically throughout the day, being highest upon waking and declining to its lowest levels of the day at the time you typically go to sleep. Chronic, moderate sleep deprivation interrupts this diurnal cycle, causing end-of-the-day cortisol levels to remain high. Over time, elevated cortisol levels can lead to insulin resistance (the body’s inability to respond to insulin’s message to store nutrients), obesity and diabetes. Elevated cortisol levels are of particular concern to menopausal and peri-menopausal women, as the combination of high cortisol and low estrogen contributes to middle-of-the-body weight gain (aka the “muffin top”).
- Leptin. Secreted by fat cells, leptin is the satiety hormone, telling your brain when you’ve consumed enough calories and reducing appetite to prevent overeating. Leptin regulation is markedly affected by sleep duration. Chronic sleep deprivation results in lower circulating levels of leptin, increased appetite and higher caloric intake, even in the absence of increased physical activity (i.e., short duration sleepers have potentially more wakeful hours to be physically active; in the studies cited above, they weren’t, either because they chose not to be or their activity was restricted by the researcher). Given that many menopausal and perimenopausal women experience insomnia and middle-of-the-night awakening, even those that attempt to get an adequate number of hours of sleep each night may not.
- Ghrelin. Working in opposition to leptin, ghrelin is secreted by the stomach and stimulates appetite. Short sleep duration is associated with elevated ghrelin production and increased hunger and appetite, in particular an appetite for foods high in carbohydrates (hello chocolate!). Similarly, declining estrogen levels (both during the period leading up to menopause and during the second half of the menstrual cycle in regularly cycling women) also trigger an increased appetite for sweet and starchy foods.
- Glucose tolerance. The sweet and starchy carbohydrates we consume are broken down, by the gut, into smaller, glucose molecules, to be used as fuel by our muscles and brain. Excess glucose is stored as fat, a process triggered by the release of insulin by the pancreas. Chronic short sleep duration results in a marked reduction in acute insulin response; glucose remains in the blood stream for a much longer period of time after consumption leading to a pre-diabetic state after as little as a week of sleep restriction.
So ‘yes’, in answer to the question posed in the title of this post, sleep does play a role in weight gain after 40. In particular when short sleep duration is frequent, consumption of starchy carbohydrates is chronic and estrogen levels are in decline.
The bottom line? In addition to paying attention to nutrition (less processed please) and adding strength training to your fitness schedule (build muscle to burn fat), developing good sleep habits appears to be key to long term health, happiness and quality of life during the midlife years. How are you going to improve yours?
Although I’ve found a number of ‘tricks’ to improving my own sleep health, I’d love to hear yours.
Do you have any pre-bedtime rituals that help you fall and stay asleep?
How do you deal with middle-of-the-night wake ups?