Large avocado study: So-so effects on bulging waistlines, cardiometabolic risk factors

Eating one avocado a day for 6 months does not appear to yield significant benefits in terms of slimming down the waist area and controlling risk factors associated with cardiometabolic disorders, according to data from Habitual Diet and Avocado Trial (HAT), which is said to the most extensive of its kind.

When added to habitual diets, daily avocado consumption for 6 months resulted in a 0.074-litre change in visceral adipose tissue (VAT), the primary study endpoint, with a difference of 0.017 litre (95 percent confidence interval [CI], −0.024 to 0.058; p=0.405) relative to a diet that was not supplemented with avocado. [J Am Heart Assoc 2022;doi:10.1161/JAHA.122.025657]

Likewise, there were no marked changes seen in other outcomes, such as hepatic fat fraction, high-sensitivity C-reactive protein, and metabolic syndrome components (ie, waist circumference, systolic and diastolic blood pressure, and triglyceride, glucose, and high-density lipoprotein cholesterol concentrations).

“While the avocados did not affect belly fat or [promote] weight gain, the study still provides evidence that avocados can be a beneficial addition to a well-balanced diet,” said one of the study authors Prof Penny Kris-Etherton, Evan Pugh University Professor of Nutritional Sciences at Pennsylvania State University, Pennsylvania, US, in a statement.

“Incorporating an avocado per day in this study did not cause weight gain and also caused a slight decrease in low-density lipoprotein cholesterol (LDL-C), which are all important findings for better health,” Kris-Etherton added.

Total cholesterol and LDL‐C levels showed modest but significant reductions (difference between avocado vs no avocado in diet: –2.9 mg/dL [p=0.026] and –2.5 mg/dL [p=0.038], respectively). Moreover, avocado consumption led to a higher diet quality, as evidenced by Healthy Eating Index improving by 8.4 points, with a significant increase in the intake of fibre (9.4 g/day; p<0.001 for all).

“The between‐group differences in total cholesterol and LDL‐C align with the observed dietary fibre differences between [the intervention] groups. A single avocado has ≈3.3 g of soluble fibre. Other factors may have also contributed to the differences in total cholesterol and LDL‐C concentrations, such as changes in the gut microbiota and the phytosterol content of the avocados,” Kris-Etherton and colleagues wrote in their study. [Food Res Int 2020;138:109774]

Overall, the findings do not support the hypothesis that avocado intake would reduce VAT, which is based on prior clinical trials reporting that diets high in monounsaturated fatty acids (MUFAs) lower the upper body fat (android and abdominal) to lower body fat (gynoid) ratio, both with and without weight loss. [Prog Lipid Res 2017;67:1-15; Diabetes Care 2007;30:1717-1723; Am J Clin Nutr 2005;82:320-326; Br J Nutr 2003;90:717-727]

However, compared with previous studies, HAT “had a larger sample size, which increased the statistical power to detect true effects if they occurred, had a longer intervention period, and employed a more realistic dietary modification, a single avocado a day with no additional dietary advice, mimicking real world conditions,” the authors pointed out.

The key takeaway, according to the authors, seems to be that “a change in dietary patterns rather than a single food or nutrient may be necessary to achieve clinically significant improvements in visceral adiposity and other cardiometabolic risk factors.”