> to achieve 10% one must in general consciously malnutitrion and avoid eating food that the body can use to synthesize fat.

No, no! If you are eating foods that humans should eat and exercising about an hour a day, you will naturally fall below 10% no matter what else you do.

I never limit the amount of food I eat and in no sense am I "malnourished". I am 80 kilos at around 8% body fat and I still have a lot to spare before it would start to affect my athletic performance as a sprinter. Go take a look at the typical 100m sprinter physique and tell me that any of them are malnourished!