The results of this study suggest that the addition of ~ ½ of a Hass avocado at a lunch meal can influence post-ingestive satiety over a subsequent 3 hour and 5 hour period in overweight and moderately obese adults. Specifically, adding avocado to a lunch meal yielded a 23% increase in satisfaction (P = 0.05) and a 28% decreased desire to eat (P = 0.04) over a subsequent 5 hour period as compared to the avocado-free control lunch meal. Also, adding avocado to a lunch meal yielded a 26% increase in satisfaction (P = 0.02) and 40% decreased desire to eat (P = 0.01) as compared to the avocado-free control lunch meal over a 3 hour period. However, an additional 112 kcal was contained in the avocado, which may have accounted for the observed increased satisfaction and decreased desire to eat. Further, a 24% decreased desire to eat (P = 0.16) and 22% increase in satisfaction (P = 0.07) was observed over a 3 hour period after consumption of the isocaloric avocado inclusive lunch test meal as compared to the avocado-free control lunch meal. However, the changes in all five measurements of appetite sensation tended to taper off after 5 hours.
Energy intake at the subsequent ad libitum dinner meal and evening snack and dietary compensation did not differ between the 3 lunch test meals, which may have been due to the 5 hour time interval between the lunch test meal and ad libitum dinner meal. De Graaf and Hulshof  have previously reported that the weight or amount of food in a preload affects subsequent appetite and food intake for only up to two hours after the preload. These findings are consistent with the findings of equivalent energy intake at the subsequent dinner meal and evening snack in the current study, yet inconsistent with changes in two specific measures of appetite sensation that we observed at both 3 and 5 hours for the avocado added test meal. Further, Flint et al.  has reported that an 8-10% difference in the response magnitude relative to control in food intake or satiety score (AUC) is of practical relevance. We found differences of practical relevance for all five appetite sensation measurements between the C versus the AI and AA interventions ranging between 11-24% and 11-40%, respectively. However, we did not find a statistically significant difference for hunger, fullness or prospective food consumption between the 3 test meals.
Our overweight participants partially compensated for energy (66%) and fat (36%) intake and overcompensated for protein (235%) and carbohydrate (118%) at a subsequent ad libitum dinner meal and evening snack when avocado (weighted mean energy = 112 kcal) was added to the lunch meal. Thus, the majority of the energy provided by the addition of avocado to the diet was offset by dietary adjustments at the ad libitum dinner meal and evening snack. Others have reported that individual daily energy intake can vary by 20 to 30 percent, and that short-term dietary manipulations of less than ~400 kcal may not heavily influence dietary energy compensation [17, 18], which may have been one of the reasons for the equivalent subsequent energy intake at the dinner meal and evening snack between the 3 study days.
There are two potential ways a whole food can be incorporated into a meal, addition or isocaloric replacement. Addition is when the food is simply added to a meal, which results in an increase in nutrients and total energy, whereas isocaloric replacement occurs when the food is included and other foods are simultaneously decreased or eliminated to compensate for the overall energy content of the meal. It is worth noting that the AUC(0-3h) for blood glucose in the current study was equivalent between the 3 lunch test meals despite the additional mean energy (112 kcal) content and additional ~7 g carbohydrate in the AA lunch test meal. Avocados contain a unique seven carbon sugar (D-manno-heptulose) that does not contribute energy, and some believe it may support blood glucose control and weight management by reducing glycolysis via hexokinase inhibition . Additionally, 30 minutes after the start of the lunch test meal the inclusion and addition of avocado significantly attenuated the rise in blood insulin levels by 37% and 22%, respectively (P = 0.04). Avocados are rich in antioxidants (e.g. polyphenolic compounds), which others have shown to be effective in improving insulin sensitivity in an overweight cohort . Hence, including or adding avocado to a dietary pattern may assist in ameliorating the postprandial dysfunction in glucose homeostasis that may be present in overweight individuals.
The AUC(0-3h) for blood insulin was lower in the AI test meal compared to both the C and the AA test meals, however this biological parameter did not significantly influence the five appetite sensation measurements between the AI and avocado-free C test meal (P = 0.07 to P = 0.64). It is worth noting that the five appetite sensation measurements for both the AI and AA test meals went in a favorable and similar direction, and borderline significant findings were found between the AI and C test meal in the context of increased satisfaction (P = 0.07) and a tendency existed towards reducing the desire to eat (P = 0.16).
Insulin and the incretin hormones covary in response to elevated postprandial glucose levels , which makes it challenging to uphold the glucostatic theory proposed by Mayer . Andersen et al. have observed that postprandial levels of blood glucose are inversely associated with self-reported appetite and food intake , however others have shown no association between satiety and blood glucose levels using an intravenous carbohydrate infusion . Thus, it is plausible that the incretin hormones were influenced by the fat and fiber from the addition of avocado to the AA test meal, which yielded an increase in satisfaction and a reduction in the desire to eat. Although fat delays gastric emptying, some studies have shown that protein in the diet has the most potent action on satiety followed by carbohydrate, and fat the least [25, 26]. However, it is important to note that studies designed to evaluate the satiety level of fat usually add fat to a meal in the form of oil or shortening, which increases the energy density of the meal without appreciably altering the volume of the meal. Thus, the low satiating effect of fat found in some studies may have been mediated exclusively by the increase in energy density.
It is also worth noting that the intake at the ad libitum dinner and evening snack was similar between the AI and AA lunch test meals, and that the inclusion of avocado at a meal along with a concurrent reduction in other foods containing similar macronutrients favorably reduced the subsequent energy intake by 83 kcal (6.5%), and reduced the protein, carbohydrate and fat intake by 3.4 g, 6.0 g and 4.9 g, respectively. Avocados are a rich source of monounsaturated fatty acids, which are preferentially oxidized and increase thermogenesis as compared to polyunsaturated and saturated fatty acids. Thus, the inclusion of avocados to a dietary meal pattern may have additional implications in weight management in an overweight population.
Although we found a significant reduction in insulin levels and favorable changes in two specific measures of appetite sensation for the AI and AA lunch test meals, respectively, we did not observe any behavioral change in dietary intake at the subsequent ad libitum dinner meal and evening snack between the 3 test meals. However, this latter null finding should not be over-interpreted as the data presented in this study are for 3 separate days (one week apart) and additional dietary energy compensation is plausible over several days and weeks .
This study had several strengths and limitations. Our controlled “laboratory” type setting had high internal validity due to the high degree of sensitivity and control over the dietary intervention and study outcome measures. An additional strength is that we analyzed the AUC appetite sensation data as opposed to a single time point because analysis of individual time points is not physiologically independent and is prone to type 1 errors. A study limitation is that we did not measure dietary intake in-between the 3 assigned study days. An additional study limitation is that we provided a wide variety of foods at our ad libitum dinner buffet meal, which is at variance with the typical eating pattern of most individuals and is likely to delay satiation and facilitate increased food intake . Lastly, we may have placed the participants in an atypical environment by not providing food to them for 5 hours.