Effects of a low-insulin-response, energy-restricted diet on weight loss and endocrinological parameter in obese, anovulatory women in their reproductive years
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There is consistent evidence that obese women are less fertile than women of normal body weight. Obesity, in particular android obesity, is associated with several sex steroid abnormalities in premenopausal women including: increased free estrogen and androgen fractions, reduced sex hormone-binding globulin and increased bioactive estrogen delivery to target tissue. The state of insulin resistance with secondary hyperinsulinemia is commonly observed in obese, infertile women whereas the gonadotrophic effects of insulin on ovarian steroid hormone synthesis have been indicated in vivo and in vitro. Insulin can directly and indirectly stimulate ovarian androgen production. The exaggerated insulin action on ovarian tissues may present the pathological mechanism for disturbances in the endocrine profile and menstrual cycle and infertility in some obese women. Due to certain limitations we did not diagnose anovulation whereas only a certain percentage of the subjects in each group were hyperinsulinemic. One of the problems experienced was the drop outs in each group. Weight loss is associated with a significant improvement in menstrual abnormalities, ovulation and fertility rates with a reduction in hyperandrogenism and hyperinsulinemia. It is suggested that weight loss should be the first option in the treatment of overweight infertile women. Intervention studies suggest that reducing weight and/or hyperinsulinemia either by diet alone or a combination of diet and drug therapy should be investigated. This study was undertaken to evaluate the effects of a low-insulin-response, energyrestricted diet (LID) on anthropometric and endocrinological parameters in obese women with menstrual abnormalities. For the purpose of this study we compared the effects LID to a normal balanced-energy restricted diet. The principles for the LID were based on the available literature regarding the insulin response to foods and their combinat ions. At baseline 37 candidates were randomly assigned into two groups. Group A followed the LID and consisted of 19 candidates whereas Group B followed the NO and consisted of 18 subjects. The inclusion criteria were: obese (BMI > 30kg/m2), premonopausal, insulin resistance, anovulation and between the ages of 18 and 04 years of age whereas the exclusion criteria included increased fasting and stimulated glucose concentrations, cigarette-smokers, and the presence of any chronic medical condition. Subject fasted for a 10 to 12 hour period after following a 250 g carbohydrate diet for three-days prior to baseline blood sampling. Blood samples were collected at baseline and at the end of the 16-week trial and analyzed for fasting insulin and glucose, testosterone (T), luteinizing hormone (LH), follicle stimulating hormone (FSH), estrogen (E), prolactin, thyroid stimulating hormone (TSH), thyroxine (FT4), leptin and progesterone. Insulin resistance were defined as a glucose-to-insulin ratio < 4.5. Stimulated 30 and 120-minute insulin and glucose were collected after subjects consumed 82.5g of monohydrate glucose powder diluted in 300ml water. Due to certain limitations we did not diagnose anovulation whereas only a certain percentage of the subjects in each group were hyperinsulinemic. One of the problems experienced was the drop outs in each group. Results form this trial indicated a significant reduction in fasting and JO-minute stimulated insulin, LH, and testosterone and leptin concentrations in the NO group whereas only leptin concentrations reduced significantly in the LID group. A significant reduction occurred in mean weight, BMI, body fat percentage, waist and hip circumference in both groups. Numerous studies evaluated the effects of weight loss on fertility but to our knowledge this is the first trial of its kind to evaluate the effects of two different test diets on fertility parameters. Results from this trial confirm the positive effects of weight loss on endocrinological and anthropometric parameters in obese women, however, the LID showed no beneficial effects over the NO. Future research is needed to evaluate the effect of diet manipulation on fertility parameters with specific regard to diet manipulation in combination with drug therapy. This trial, however, serves as a good pilot study for future research of this kind.