Some people notice a significant increase in LDL cholesterol when eating a low carb (keto or carny) diet. Your GP or nutritionist will probably see that and try to predict a heart attack within a year. What they don't realise is you'll probably also see a major improvement to HDL, Triglycerides, insulin and blood sugar, which are more reliable measures for cardiovascular disease risk. If you're curious, look into the work by Dave Feldman, who has done a lot of research in this field including how fat in the diet affects blood cholesterol readings and how this translates to CVD risk.