Is a very low-calorie diet the answer to Polycystic Ovary Syndrome (PCOS)?

A recent Nutrients study compared the effects of a very low-calorie diet (VLCD) to a moderate energy deficit diet in obese women with polycystic ovary syndrome (PCOS). 

Study: The Effect of a Very-Low-Calorie Diet (VLCD) vs. a Moderate Energy Deficit Diet in Obese Women with Polycystic Ovary Syndrome (PCOS)—A Randomised Controlled Trial. Image Credit: Pormezz/Shutterstock.comStudy: The Effect of a Very-Low-Calorie Diet (VLCD) vs. a Moderate Energy Deficit Diet in Obese Women with Polycystic Ovary Syndrome (PCOS)—A Randomised Controlled Trial. Image Credit: Pormezz/


PCOS is one of the most common endocrine disorders prevalent in reproductive-aged women. Hyperandrogenism and insulin resistance (IR) are two key features of PCOS, which results in several clinical outcomes, including acne, polycystic ovary morphology on ultrasound, and hirsutism.

Furthermore, PCOS causes complications during pregnancy and anovulatory infertility.

Women with PCOS are also at a higher risk of metabolic diseases like type 2 diabetes mellitus (T2DM) and cardiovascular disease. These women experience high depression, anxiety, and lower life quality.

Women with PCOS also experience difficulties in maintaining healthy body weight. A recent longitudinal study estimated that 75% of women with PCOS are overweight or obese.

Weight management and lifestyle modifications are the two most common first lines of therapy for PCOS. A proper diet, regular physical activity, and behavioral changes could alleviate several PCOS-related outcomes.

Although many low-energy diets are followed for weight loss by women with PCOS, with or without anti-obesity/anti-diabetes medication, the effectiveness of very-low-calorie diets (VLCDs) in this population needs more clarity.

VLCDs are associated with an intake of less than 800 kcal per day. This diet partially or completely replaces meals with synthetic alternatives, such as soups, bars, or shakes containing sufficient nutrients. Rapid weight loss occurs due to extreme caloric restriction involved in VLCDs.

A previous study had shown that the use of VLCDs in adults with T2DM had resulted in increased insulin secretion and reduced HbA1c levels to pre-diabetic and normal levels.

About the study

The current randomized, open-label study compared the effects of a VLCD to conventional energy deficit diet on body weight, androgen levels, other hormone levels, and metabolic parameters in obese women with PCOS.

The current study was conducted at the Academic Diabetes, Endocrinology, and Metabolism Research Centre at Hull Royal Infirmary.

Participants diagnosed with PCOS wanting to lose weight were recruited between the ages of 18 and 45. Participants with hyperprolactinemia, non-classical 21-hydroxylase deficiency, androgen-secreting tumors, and Cushing’s disease were excluded.

Additionally, participants who lost more than five kilograms of weight within the last six months were breastfeeding, pregnant, attained menopause or perimenopause, substance abuse, and those with a history of chronic diseases were excluded. Eligible candidates were subjected to non-hormonal contraception throughout the study period.

Participants were screened based on the eligibility criteria during the first visit (visit one). All eligible candidates were randomly assigned to either VLCD or moderate calorie (a conventional) diet group for sixteen weeks.

The study timeline was divided into eight weeks of intervention, followed by eight weeks of diet reintroduction and follow-up. Visit two (baseline) was conducted within four weeks of visit one, where participants underwent anthropometric evaluation and blood samples were collected.

Participants were reviewed two weeks after the commencement of interventions (visit three). All participants were evaluated every two weeks (visits 4, 5, 7, 8, and 9). 

Study findings

A total of 63 women with PCOS were screened, out of which 23 candidates were excluded as they did not fulfill all eligibility criteria.

Finally, 21 women were placed in the VLCD arm and 19 in the conventional energy deficit diet group. It must be noted that eleven candidates from each group completed the 8-week follow-up.

Interestingly, both interventions resulted in short-term weight loss with positive changes in body composition. However, compared to a conventional energy-deficient diet, VLCD caused a greater weight reduction and significant improvements in the participants’ hyperandrogenaemia, body composition, and metabolic parameters.

These improvements could substantially improve the quality of life, ovulation, menstrual irregularities, hyperandrogenaemia, and emotional well-being of this population.

Participants in the VLCD arm reduced around 11% their initial body weight after eight weeks of intervention. Furthermore, a mean weight loss of 16% was recorded in women who completed the 16-week follow-up.

Comparatively, participants who followed a conventional energy deficit diet underwent ~3.9% weight loss from baseline to 8 weeks. This finding highlights that VLCD is more effective in reducing weight in obese women with PCOS. 

A previous study used commercial products for an energy-restricted diet (1000–1200 kcal/d), which showed positive weight reduction. However, the amount of weight reduced was much less than the participants of the VLCD arm at the same time period. 

A significant 32% reduction in free androgen index (FAI) was observed in the VLCD arm, while a non-significant 8% reduction was recorded in the conventional energy deficit arm.

The weight reduction after eight weeks in both interventions was due to improvements in total and trunk fat masses and reductions in fat-free body mass (FFM).

The overall improvements in hyperandrogenism and obesity mediated by VLCD alleviated metabolic dysfunction and other complications in women with PCOS.


The current randomized controlled trial revealed that both interventions could effectively reduce body weight.

However, compared to a conventional energy deficit diet, VLCD is more effective in weight reduction and causes significant improvements in metabolism, body composition, and hyperandrogenism in women with PCOS, with relatively few side effects. In the future, the findings of this study must be validated using a larger sample size.