Authors: Michelle Wien; Ella Haddad; Keiji Oda; Joan Sabaté, Loma Linda University
Study Summary
A randomized crossover feeding study on 26 healthy, overweight adults, conducted at Loma Linda University, was published in the November 2013 Nutrition Journal. The study evaluated whether incorporating fresh Hass avocado in a lunch — either by replacing other foods or by simply adding it to the meal — would influence satiety, blood sugar and insulin response and subsequent food intake.
Participants ate the same standardized breakfast followed by three different lunch meals on three different days:
- Standard (control) lunch: without avocado (designed to meet individual meal-based calorie and macronutrient needs) that included a salad with Italian dressing, a baguette, and cookies.
- Avocado replacing part of the Italian dressing and cookies lunch: the same standard lunch with approximately one-half of a fresh avocado in place of part of the Italian dressing and cookies (the same total energy and macronutrient content of the standard lunch).
- Avocado added to a standard lunch: the same standard lunch with approximately one-half of a fresh avocado added (total higher calories and macronutrients).
The study found that when approximately one-half of a fresh avocado was added to a standard lunch, participants felt more satisfied and had a reduced desire to eat following the meal, than when a standard lunch with no avocado was eaten. When the avocado was added to a standard lunch or replaced part of the Italian dressing and cookies in a standard lunch, the immediate post-meal rise in insulin levels was significantly lower than when a standard lunch with no avocado was eaten. No matter which lunch was eaten, the calories consumed throughout the remainder of the day were equivalent.
While the conclusions drawn from this study are too limited to apply to the general public — due to the study size and study limitations noted by the researchers — the results do provide promising clues and a basis for future research to determine avocados’ effects on satiety and glucose and insulin response.
Standard Lunch Results
After 26 healthy, overweight people ate the avocado added to a standard lunch:
They had a reduced desire to eat after the meal compared to eating the standard lunch. The half avocado added to a standard lunch significantly decreased the desire to eat by 40 percent over a three-hour period compared to the standard lunch and decreased the desire to eat by 28 percent over a five-hour period compared to the standard lunch.
Participants felt more satisfied after the meal compared to eating the standard lunch. The half avocado added increased self-reported subjective feelings of satisfaction by 26 percent over a three-hour period compared to the standard lunch.
The number of calories and macronutrients consumed at subsequent meals was not statistically different compared to when they ate the standard and avocado-replacing part of the Italian dressing and cookies lunches.
At 30 minutes after the start of the test meal, the avocado added to a standard lunch helped mitigate rises in insulin compared to eating the standard lunch. However, there was no significant difference in insulin levels over a three-hour period. The rise in insulin levels was significantly weakened by 22 percent 30 minutes after the start of the meal, compared to eating the standard lunch. There was also no increase in blood sugar levels beyond what was observed after eating the standard lunch, despite the extra calories and carbohydrates provided by the added avocado.
There was no increase in blood sugar levels beyond what was observed after eating the standard or avocado-replacing part of the Italian dressing and cookies lunches. Adding approximately one-half of a Hass avocado to a standard lunch did not affect blood sugar any more than the standard lunch or avocado replacing part of the Italian dressing and cookies lunch, despite the extra calories and carbohydrates provided by the added avocado.
Results When Avocados Replaced Part of the Italian Dressing and Cookies from a Standard Lunch
After 26 healthy, overweight people ate the avocado-replacing part of the Italian dressing and cookies lunch: The number of calories and macronutrients consumed at subsequent meals was not statistically different compared to when they ate the standard and avocado added to a standard lunch. It helped mitigate the post-meal rise in insulin compared to eating the standard lunch. Thirty minutes after the start of the meal, the rise in insulin levels was significantly weakened by 37 percent, compared to eating the standard lunch. And, blood insulin remained significantly lower over a three-hour period compared to when the standard lunch was eaten.
Researchers concluded that the reduction in the rise in insulin levels observed with the avocado-replacing part of the Italian dressing and cookies lunch is worthy of future exploration in persons with insulin resistance (e.g. metabolic syndrome) and type 2 diabetes to determine if eating avocados can favorably influence glucose homeostasis.