Brain Tumor Removal and Calorie Restriction Show Benefits for Blood Sugar Control

A study published in JAMA Network Open found that removing olfactory groove meningioma — a type of brain tumor located near the base of the brain — may improve blood sugar control in patients with diabetes. In a separate study submitted to Clinical Nutrition ESPEN, both continuous and intermittent calorie restriction were found to improve metabolic health in type 2 diabetes, with adherence emerging as a key factor in real-world success.

Researchers followed patients with an olfactory groove meningioma and diabetes over five years after surgery, tracking long-term changes in hemoglobin A1c (HbA1c), a standard measure of blood sugar control, and body weight after tumor removal surgery. The research team found that blood sugar control improved after tumor removal in most patients, improvements often happened soon after surgery and lasted for years, many patients also lost weight after surgery, and improvements occurred even when diabetes medications stayed the same. This type of brain tumor affects both frontal lobes simultaneously and is usually thought of as causing symptoms like vision problems, personality changes or loss of smell. The study authors stated, 'What surprised us was how much blood sugar control improved after surgery in many of these patients. The findings may help us better counsel patients before surgery and raise new questions about how the brain influences metabolism throughout the body.' The findings suggest that some brain tumors may affect the body's ability to regulate metabolism and blood sugar, and that removing certain brain tumors may improve blood sugar control and weight in some patients with diabetes, in addition to improving neurological symptoms.

The calorie-restriction study evaluated how a three-month continuous calorie-restricted (CCR) diet compared with an intermittent calorie-restricted (ICR) diet affects body composition and resting energy expenditure in adults with type 2 diabetes and overweight or obesity. It was a post-hoc analysis combining participants from two separate randomized trials rather than a direct head-to-head randomized comparison. The CCR group consumed approximately 750 kilocalories per day from meal replacements, with low-carbohydrate vegetables provided in addition to lean protein, low-energy drinks, and skim milk. The ICR group followed an early time-restricted eating pattern, consuming all calories between 8:00 AM and 6:00 PM, with a daily intake of 1300 kilocalories for women and 1500 kilocalories for men, alongside moderate carbohydrate restriction.

The analysis included 67 participants: 41 in the CCR group and 26 in the ICR group. The average age was approximately 60 years, and more than half were women. After three months, both diets produced significant weight loss, with CCR participants losing 7.4 kg on average and ICR participants losing 6.8 kg. Both groups showed significant reductions in body mass index and waist circumference. Fat mass decreased significantly in both groups. The percentage of fat-free mass increased in both interventions, although absolute fat-free mass declined modestly in the ICR group, representing approximately 20 percent of total weight loss. Resting energy expenditure decreased significantly only in the CCR group, which may reflect adaptive thermogenesis rather than solely fat-free mass loss.

More than 500 million people worldwide live with type 2 diabetes, and excess weight remains one of its most significant causes. The researchers noted that between-group comparisons were exploratory and not powered for definitive conclusions, and the intervention lasted only three months, limiting conclusions about long-term sustainability.