Long-term adherence to a mostly plant-based diet is associated with lower levels of leptin and insulin, greater blood glucose control, and favorable changes in markers for obesity. This is according to a study published in the Journal of Nutrition.
The Biological Mechanisms Behind a Plant-Based Diet and Diabetes, Obesity
The study was a cross-sectional analysis of patient data from The Nurses’ Health Study II. In total, the researchers randomly selected 831 women (mean age, 45 years; body mass index, 24.6 kg/m2) from the study who had 2 blood samples collected from 1996 to 1999 and 2010 to 2011. Researchers examined the association between a plant-based diet and diabetes, obesity, and inflammatory markers. The following markers in participants’ plasma were analyzed:
- Adiponectin: protein hormone marker that regulates blood glucose and reduces inflammation
- Leptin: protein produced by adipose cells that inhibits hunger and acts as a proinflammatory cytokine
- Soluble leptin receptor (sOB-R): partly regulates leptin’s biological activity
- Insulin: peptide hormone responsible for transporting glucose into cells; increased and unregulated levels in the body associated with insulin resistance and obesity
- Retinol-binding protein-4 (RBP-4): adipokine responsible for transporting retinol; frequently increased in patients with insulin resistance (ie, type 2 diabetes)
- High-sensitivity C-reactive protein (hsCRP): protein that is elevated in response to inflammation; increased levels associated with abdominal fat
- Interleukin-6 (IL-6): acts as a pro-inflammatory cytokine and anti-inflammatory myokine
Semiquantitative food frequency questionnaires administered at each blood collection were examined to identify 3 plant-based diet indices. These indices included an overall plant-based diet index (PDI), healthful plant-based diet index (hPDI), and an unhealthful plant-based diet index (uPDI). The hPDI represented a high-quality diet consisting of whole grains, fruits, vegetables, and nuts that was also low in sweets and refined grains.
Plant-Based Diet Reduces Markers for Diabetes, Obesity, and Inflammation
Participants with higher hPDI — ie, those who consumed higher amounts of plant foods and low amounts of sugar and refined grains — had significantly lower plasma concentrations of leptin, insulin, and hsCRP as well as higher levels of adiponectin and sOB-R (biomarker differences per 10-point higher hPDI, −7.2% for leptin; −10.0% for insulin; −13.6% for hsCRP; 3.0% for adiponectin; and 1.9% for sOB-R; p≤0.025).
Conversely, individuals with higher uPDI, which represented a diet consisting of more sweets and refined grains and lower amounts of plant-based foods, had higher leptin (4.4%) and insulin (4.8%) concentrations (p≤0.048). Over time, increases in hPDIs inversely correlated with changes in leptin and hsCRP (biomarker changes per 10-point hPDI increase, −7.7% for leptin and −17.8% for hsCRP; p≤0.005), according to multivariable-adjusted analyses. Additionally, increases in uPDI over time positively correlated with changes in leptin (10.1%), hsCRP (13.5%), and IL-6 (12.4%) concentrations (p≤0.021).
Limitations and Recommendations
Limitations of this study were the inclusion of mostly Caucasian nurses without metabolic diseases as well as the use of self-reported questionnaires to obtain participants’ dietary data.
Despite these limitations, this study adds to the existing literature that suggests a mostly plant-based diet is associated with lower risk factors for cardiovascular disease, including obesity and diabetes. According to the researchers, these data presented in this cross-sectional analysis “corroborate the recommendation that increasing the intake of healthy plant foods and reducing the intake of less healthy plant foods simultaneously would be essential for the prevention of cardiometabolic diseases.”
Baden MY, Satija A, Hu FB, Huang T. Change in Plant-Based Diet Quality Is Associated with Changes in Plasma Adiposity-Associated Biomarker Concentrations in Women. J Nutr. 2019;149(4):676-686.