It is easy to assume that high-calorie foods should always be avoided. But research continues to show that some calorie-dense foods, such as nuts, avocados, peanut butter, and Greek yogurt, can help lower cholesterol or stabilize blood sugar. However, some recent follow-up studies have found smaller effects than earlier research, prompting suggestions that the actual effect of each food should be examined separately.
According to the medical community on the 24th, a team led by Professor Jordi Salas-Salvado at Rovira i Virgili University in Spain recently conducted a meta-analysis statistically synthesizing data from 113 nut-related trials and 8,060 participants published to date.
The results showed that the group that ate an average of 45.5 grams of nuts per day saw reductions in total cholesterol, bad cholesterol (LDL), and triglycerides. 45.5 grams is about a handful. The study was supported by the International Nut and Dried Fruit Council (INC), a nut industry group.
The reductions were 0.14 mmol/L for total cholesterol, 0.12 mmol/L for LDL, and 0.05 mmol/L for triglycerides. However, there was no change in good cholesterol (HDL). While bad cholesterol decreased, no effect of increasing good cholesterol was confirmed.
An analysis synthesizing 28 studies that tracked 1.89 million people across several countries found that the group that ate a lot of nuts and seeds had a 19% lower risk of cardiovascular disease and a 23% lower risk of cardiovascular death than the group that ate little. However, the researchers stated that the reliability of the evidence was mostly at the "low" or "very low" level. This means that people who eat a lot of nuts may also tend to be healthy in other lifestyle habits, making it difficult to conclude that the effect is attributable to nuts alone.
For avocados (200-300 kcal each, similar in calories to a bowl of rice), the differences in results between studies are greater. A 2016 study found that the group that ate avocados saw reductions of 18.80 mg/dL in total cholesterol, 16.50 mg/dL in LDL, and 27.20 mg/dL in triglycerides.
In contrast, follow-up studies published in 2024-2025 produced more limited results. One study found no significant changes in triglycerides, total cholesterol, HDL, or fasting blood sugar, with only LDL decreasing by 3.75 mg/dL. A 2025 paper that re-examined existing studies found that LDL decreased by 9.4-17 mg/dL only in people who already had high cholesterol, and there was no difference in people with normal cholesterol. This means it may help people with high cholesterol, but the effect is not clear for people with normal levels.
Peanut butter is classified as a food that raises blood sugar slowly. Its glycemic index (GI, out of 100), which indicates how quickly a food raises blood sugar, is only 14. In a 2019 U.S. study, when 16 healthy adults were fed two slices of white bread and 250 mL of apple juice, blood sugar rose by 51.0 mg/dL, but when two spoonfuls (32 grams) of peanut butter were added to the same food, the increase was reduced to 35.8 mg/dL. However, it was a small study with only 16 participants.
For Greek yogurt (about 90 kcal per 100 grams, higher than the 60 kcal of regular yogurt), the effect of controlling intake through satiety has been reported more than cholesterol improvement. In one study, the group that ate high-protein yogurt as a snack showed increased secretion of the appetite-suppressing hormone (PYY) and a tendency to eat less at the next meal. Greek yogurt is made by removing whey from regular yogurt and concentrating the protein, and the increased protein content in this process is interpreted as leading to satiety.
These studies share a common premise. Most measured the effect of replacing saturated-fat foods such as pork belly or butter, or refined carbohydrates such as white bread, with nuts or avocados. This differs from adding them on top of an existing diet. If this premise is left out and only the result that "it is good for the body despite being high in calories" is accepted, it could be misunderstood as meaning one can eat unlimited amounts.
