By Sheri Colberg, PhD
Before the advent of blood glucose meters, discovering how much of an effect female hormones have on insulin action was impossible. If you’re female, past puberty, and still young enough to be menstruating, then you’ll want to find out more about factoring your time of the month into your insulin adjustments. Moreover, if you’re pregnant, diabetic, and active, you’ll also be facing some special circumstances.
How Monthly Cycles Affect Insulin Action
A woman’s normal monthly cycle has two phases: (1) follicular, which goes from the start of menses up to ovulation at midcycle, and (2) luteal, spanning the time from ovulation to your next period. Women are generally more insulin resistant during the luteal phase because of the greater release of certain female hormones (estrogen and progesterone) during that time. Such changes can also affect female athletes who have this additional factor to work into the equation to achieve balanced blood sugars while having an active lifestyle.
For example, Betty F., a regular diabetic exerciser from Toronto, Ontario, finds that her blood sugars start to increase gradually 7 to 10 days before her menses and then instantly decrease the day her period starts. To compensate, she has to increase her basal insulin (Levemir) by 1 unit a day starting a minimum of 5 days beforehand, which means that her total basal dose goes from 16 units up to 23 during that time, including an occasional 1-2 unit increase in her nighttime dose. Similarly, Cynthia F. from Chicago, Illinois, finds that she must increase her total insulin by 150 percent 3 days before her menses begin (and she still struggles to maintain control during that time), causing the changes she makes for each workout to vary. Not all women are affected equally, though, and the differences appear to be tied in with actual increases in estrogen levels; the higher they go, the more effect they have on blood sugars.
Use of oral contraceptives can alter the normal hormonal changes in women as well. Most of these pills or treatments are now made up of low-dose estrogen and progestin. Since they prevent ovulation, insulin action may be somewhat reduced, but at least it remains more balanced over the monthly cycle, leading to greater predictability and easier glucose control for most women who use them.
Being Pregnant, Diabetic, and Active: The Ultimate Challenge for Women
Even if you’re athletic and regularly active, the release of the same hormones during pregnancy as you have during the luteal phase of your menstrual cycle ensures that your insulin needs will go up while you’re expecting. Raging hormones during the third trimester in particular work to make the mother-to-be insulin resistant and spare glucose for the fetus. Being active, though, will keep you from having to raise your insulin doses as much, even during the last few months of your pregnancy. Being active will also prevent excessive weight gain and keep you from getting out of shape. If you have to stop exercising during your pregnancy for any reason, expect your insulin needs to go up dramatically, both from the hormones released and from the decrease in your insulin action that you will experience from being inactive.
Pregnancy increases the energy costs of doing any activity, so you will be using more calories during all your activities, particularly the weight-bearing ones. Your exercise intensity will likely go down, particularly in the later stages of your pregnancy as Mother Nature takes care of your baby’s health by not making it possible for you to work out as hard as normal (even if you try to). You should avoid certain activities when pregnant—contact sports, sports with lots of directional changes (like racquetball), water skiing, and cycling outdoors (when balance becomes an issue)—but you can continue doing most other ones. During the third trimester, consider substituting non-weight-bearing activities like aquatics and stationary cycling for running or doing excessive amounts of walking. Also, don’t do any exercises lying flat on your back past the second trimester because doing so can reduce blood flow to your developing baby. Despite all these changes, you will likely find that diabetes control is the least of your problems when you’re pregnant, especially if you are able to stay active.
Sign up for the Diabetes "Fit Brain, Fit Body!" fitness/lifestyle programs or for 5 free Healthy Living Reports at www.lifelongexercise.com, and access more articles and information at www.shericolberg.com. If you need tips for getting safely started on an exercise program, check out The 7 Step Diabetes Fitness Plan. For people with any type of diabetes who are already more active, consult the Diabetic Athlete’s Handbook.