The Loss Of The Menstrural Cycle On Low Carbs

Menstrual irregularities, including the loss of the menstrual cycle and a sporadic menstrual cycle, can be the result of a low-carb diet or any severe diet, malnutrition, intense exercise and athletic training and insufficient body fat. A woman has amenorrhea if she has had menses before but currently has fewer than four menstrual periods per year. Oligomenorrhea is a sporadic menstrual cycle, with three to nine periods per year. A 1996 study published in "Minerva Ginecologica" found that as many as 70 percent of female athletes experience menstrual irregularities.

Body Fat

Women require more body fat than men to maintain the functions of their reproductive system. Where top male athlete body fat standards are between 7 to 10 percent, top female athletes are between 12 to 18 percent body fat. Excluding the top tier of Olympic-level athletes, the standard range of body fat for women athletes is between 20 to 25 percent. In fact, up to 28-percent body fat is considered acceptable for non-athlete women. If your low-carbohydrate diet -- or any other diet -- contains insufficient nutrition to maintain an adequate level of body fat, you are likely to experience menstrual disruption.

Body Weight

Low body weight is another indicator of inadequate nutrition and is a good predictor of low body fat. Amenorrhea is associated with a 10- to 15-percent reduction below ideal body weight. Your ideal body weight is calculated by allowing for 100 lbs. for the first 5 ft. of height and adding 5 lbs. per inch above 5 ft. That means a woman who is 5 ft., 5 inches tall and has a medium-sized frame has an ideal body weight of 125 lbs. For women with large frames, add 10 percent. For women with small frames, subtract 10 percent. Taking into account varying frame sizes, the ideal body weight range for a woman who is 5 ft., 5 inches tall is 112 to 138 lbs.

Ketogenic Diet

When you consistently eat a very-low-carbohydrate diet, your body is forced to metabolize the fat and protein in your food and your body stores for energy. Because the body is primarily equipped to metabolize carbohydrates for its preferred energy source, the process of converting fat and protein to glucose creates excess metabolic waste known as ketones. Thus, a very-low-carbohydrate diet is sometimes called a ketogenic diet. In a 2003 study published in "Epilepsia," 45 percent of female subjects on a ketogenic diet developed menstrual dysfunction -- including amenorrhea.

Menstrual Dysfunction and Osteoporosis

Menstrual dysfunction is not simply a problem of fertility. During amenorrheic time periods, a woman does not store enough minerals in her bones, leading to osteopenia, osteoporosis and bone fractures. According to Keen and others, the bone loss that amenorrheic females suffer is irreversible even if they return to normal menstrual function. The lumbar bone density of formerly amenorrheic females in the Keen study was only 85 percent of the lumbar bone density of females who were never amenorrheic.