Hormonal and metabolic effects of diet and physical exercise in overweight/obese women with polycystic ovary syndrome

Background: Overweight/obese women with polycystic ovary syndrome (PCOS) often have hormonal problems characterized by irregular menses and decreased fertility. In addition, the overweight/obese women carry metabolic disturbances with a long-term risk of type 2 diabetes and cardiovascular disease.

Aims: The purpose of the study was to imply an individualized intervention employing either diet, exercise or the combination of both, to disentangle which of these treatment options that show the most favorable outcome in terms of hormone levels, menstrual regularity and ovarian function. Furthermore, effects on metabolic outcome variables were evaluated.

Methods: In a randomized comparative study, 57 overweight/obese PCOS women were assigned to an intervention program with either diet, exercise or the combination of both for a period of four months. The goal was to reduce the food intake by 600 kcal and increase the physical activity to 45–60 minutes of moderate to vigorous training 2–3 times per week. All patients were monthly monitored for adherence to the intervention program by either a dietician or physiotherapist, and subjected to a long-term evaluation after 12 months or more. Menstrual bleedings were recorded and ovarian parameters evaluated by ultrasound. The specific endocrine measurements consisted of changes in estradiol, progesterone, 17-OH-progesterone, luteinizing hormone, follicle stimulating hormone, sex hormone binding globulin, and dehydroepiandrosterone, as well as fasting glucose and oral glucose tolerance test, insulin, insulin-like growth factor-I, IGF-I binding protein 1 and serum levels of total cholesterol, high density lipoprotein, low density lipoprotein (LDL), triglycerides and C-reactive protein. Calculations were made for Homeostasis Model of Assessment (HOMA) index and free androgen index. Dual-energy X-ray absorptiometry was used to evaluate body composition. The values are presented as means ± standard deviation, or 95% confidence interval, or as medians with interquartile range. The data was evaluated using intention to treat or per protocol approach.

Results: There were no differences between the three groups at baseline. None of the participants were diabetic, but the majority displayed a HOMA index exceeding 3, indicating insulin resistance. The most important dietary change during the study was a reduced energy intake with more fiber, and less saturated fat and trans fatty acids based on the Swedish Nutritional Recommendations Objectified. Physically activity increased significantly in the exercise group as assessed by the number of steps per day. The summarized effects of the lifestyle interventions showed that dieting was the most effective way to reduce body weight excess, endocrinological and metabolic disturbances. Exercise alone was less effective but was superior to reduce upper body fat and maintain lean body mass. The combination of diet and exercise was too pressing for many women to pursue the intervention program in full. However, the three lifestyle interventions were equally effective in normalization of menstrual pattern and ovulation. Furthermore, there was an amelioration of the biomarkers of hyperandrogenism primarily in the diet group. Metabolic biomarkers including HOMA index, total cholesterol and LDL also improved in this group. The strongest factor to predict a reduction of BMI was increased fiber intake, while a decrease in trans fatty acid intake predicted reduced insulinogenic index.

Conclusion: Dietary management and exercise, alone or in combination, are equally effective in improving reproductive function in overweight/obese women with PCOS. However, diet alone was more effective than the other interventions to improve the general metabolic disturbances. Increased fiber and reduced trans fatty acids intake are primary predictors of metabolic improvement and weight control.

List of scientific papers

I. Nybacka Å, Carlström K, Ståhle A, Nyrén S, Hellström PM, Hirschberg AL. Randomized comparison of the influence of dietary management and/or physical exercise on ovarian function and metabolic parameters in overweight women with polycystic ovary syndrome. Fertil Steril. 2011;96:1508-1513.
https://doi.org/10.1016/j.fertnstert.2011.09.006

II. Nybacka Å, Hellström PM, Hirschberg AL. Increased fibre and reduced trans fatty acids intake are primary predictors of metabolic improvement in overweight polycystic ovary syndrome – substudy of randomized trial between diet, exercise and diet plus exercise for weight control. Clin Endocrinol (Oxf). 2017;87:680-688.
https://doi.org/10.1111/cen.13427