A study published in 2006 in the Journal of Medicinal Food explored the effects of grapefruit on weight loss and insulin resistance. Over the course of 12 weeks, 91 obese participants were divided into four groups: one received a placebo, one consumed half a fresh grapefruit before each meal, another drank 8 ounces of grapefruit juice before meals, and a final group took a grapefruit capsule prior to eating.
The results showed that grapefruit had a notable impact. All three grapefruit groups—juice, capsule, and fresh fruit—lost more weight than the placebo group. However, the group consuming fresh grapefruit experienced the most significant weight loss overall.
In addition to supporting fat loss, fresh grapefruit also improved insulin sensitivity. The study noted a marked reduction in two-hour post-glucose insulin levels in the fresh grapefruit group compared to the placebo group. The researchers concluded that eating half a grapefruit before meals was associated with both weight loss and improved insulin resistance.
What makes this particularly interesting is that grapefruit appeared to help regulate insulin and blood sugar levels—even though it contains natural sugars. These findings are similar to those from other research on citrus fruits, such as lemon juice, which has also been shown to reduce the post-meal blood sugar response.
