Hormones are like chemical messengers that get released into your bloodstream and tell your cells how to behave. Hormones help you grow, fight disease, enable you to reproduce, and affect your appetite, metabolism and weight. Scientists are increasingly recognizing the significance of hormones to your weight, which adds another nuance to the calorie-in, calorie-out approach to weight loss. Although you can't run to the pharmacist and pick up weight-controlling hormones, you should always ask your doctor to check your levels to determine whether they are impacting your weight and what you can do about them.
Leptin
Leptin is a hormone that your fat cells express while you're sleeping. One of leptin's main roles is to tell your brain to diminish your appetite when you've had enough to eat. It is also an energy regulator. That means it helps burn off extra calories to keep your weight stable. However, some people are leptin resistant, meaning the hormone doesn't work as expected. Add to that the fact that some fructose-containing foods never even tip off leptin that you've taken in a lot of calories and it's time to stop eating. Scientists have yet to figure out how to tap into leptin's obesity-fighting powers as in some cases, injecting the hormone works for some, but not others.
Ghrelin
Think of ghrelin as a gremlin, say Drs. Michael Roizen and Mehmet Oz in "You On a Diet: The Owner's Manual for Waist Management." When your stomach is empty, it stimulates the release of ghrelin, which makes you want to eat. Ghrelin can also slow down your metabolism and dial back your ability to burn fat. Overweight people tend to have less ghrelin than normal weight individuals, but Weight Watchers reports that overweight people may have more ghrelin receptors, so less hormone is needed to trip them off. The stomach secretes ghrelin every half-hour, and when you're hungry that speeds up to every 20 minutes. You can't resist the urge to eat indefinitely, which is why deprivation dieting is doomed to failure.
Insulin
One of insulin's main jobs is to help regulate your blood sugar, but it also directs fat "traffic" in your body. It inhibits the breakdown of fat and promotes the creation of fatty acids in your liver. Colorado State University states that insulin is a fat-sparing hormone. That means it tries to protect fat from being used as a source of energy.
Cortisol
Cortisol is a steroid hormone that mainly works as part of you your stress-response system. Drs. Roizen and Oz write that cortisol overstimulates your adrenal gland, which then releases too much testosterone and estrogen. Not only does this set you up for overeating, but it also promotes belly fat. Worse, cortisol decreases your insulin sensitivity, so chronic stress can be a foreteller of diabetes.
Thyroid
Thyroid hormone regulates your metabolism. Specifically, it affects your basal or resting metabolic rate. This refers to the calories your body spends to keep you alive with activities such as breathing and pumping blood. This part of your metabolism accounts for 60 to 75 percent of all the calorie burning you do. The American Thyroid Association states that people who have low levels of thyroid hormone tend to have sluggish metabolisms. Hypothyroidism, however, is only associated with a modest weight gain of approximately 5 to 10 pounds, states the association. That weight is an accumulation of extra salt and water, not fat.
References
- "You On a Diet: The Owner's Manual for Waist Management"; Michael Roizen and Mehmet Oz; 2006
- Weight Watchers: Leptin, Ghrelin, Cortisol and Weight
- Colorado State University Endocrine Index: Leptin
- Colorado State University Endocrine Index: Physiologic Effects of Insulin
- "Journal of Clinical Investigation"; Low-Dose Leptin Reverses Skeletal Muscle, Autonomic, and Neuroendocrine Adaptations to Maintenance of Reduced Weight; Michael Rosenbaum et al.; Dec. 2005
- American Thyroid Association; Thyroid and Weight; 2005
