| Olive oil is not a healthy fat (as much as I'd love it to be) -- it's got a substantial amount of saturated fat, and the interviewer is correct -- it's very easy to get a lot of empty calories with oil. Aside from that, weight is not the only issue. A high fat diet (even a vegan one) is not good for your cardiovascular system. There's a widely quoted study by high-fat diet proponents comparing two groups eating a high-fat Mediterranean diet (one with olive oil, one with nuts) to a "low fat" control group: https://www.nejm.org/doi/full/10.1056/NEJMoa1200303?query=re... This study can't really be used to advocate a high fat diet, though, because all the diets (even the control group) were actually high fat. Looking at page 28 of the appendix (https://www.nejm.org/doi/suppl/10.1056/NEJMoa1200303/suppl_f...) shows that the fat intake of all three groups was really very similar -- about 41% calories from fat for the olive oil and nut groups, but only...37% fat from the control group. 37% calories from fat is not "low fat". On the other hand, a true low fat diet, with fewer than 10% of calories from fat, has been shown to actually reverse the progression of heart disease: https://www.ncbi.nlm.nih.gov/pubmed/7500065 (this was one of the first studies to demonstrate this, but they've repeated this with larger groups and gotten the same results) |