wefast silicon valley fasting club 0540Melia Robinson

The ketogenic or "keto" diet has been called the holy grail of good health and weight loss by some doctors and bloggers. On the flip side, it's a nutritionist's nightmare.

The keto diet goes against conventional wisdom on health eating. It encourages eating lots of fat and limits carbohydrates to no more than 50 grams a day, the rough equivalent of a plain bagel or a cup of white rice. By comparison, dietary guidelines laid out by the US Department of Agriculture recommend consuming between 225 and 325 grams of fluffy, white carbs a day.

Tech workers from internet entrepreneur Kevin Rose to podcaster Tim Ferriss swear by the keto diet. Some supporters of the diet say it gives them a mental edge in the workplace.

Here's why health nuts in Silicon Valley are saying yes to fat.