A lot of the Silicon Valley elite are doing extreme experiments on their bodies in hopes of prolonging their lives and improving their health. The latest fad among this set is sticking to a so-called 'ketogenic' diet that's exceptionally high in fat and low in carbs and is considered an experimental treatment for diabetes. Think Atkins, but way more extreme.

Ambar Bhattacharyya, a managing director with Maverick Ventures, initially embarked on a low-carb, high-fat "ketogenic" diet during the due diligence process for a startup called Virta Health. The diet was designed to transition his body to burning fat as its primary fuel source, rather than glucose. Those on the diet typically eat less than 30 grams of carbs each day.

He lost about 7 pounds in the first week, but gave up after a few months. "I started to get really cranky and had to drink a lot of coffee," he recalled. "That meant a lot more bathroom breaks during our partner meeting."

Bhattacharyya said that two other investors at the office tried it, meaning about a third of the office was on ketogenic diets.

Virta, the company that caught Bhattacharyya's interest, is geared at helping people with type 2 diabetes get off their meds by coaching them to adopt lifestyle changes, including carb restriction. Its doctors have mixed feelings about body-hacking venture capitalists trying to get into nutritional ketosis, without supervision.

"If you only try it for a month, you aren't reaping the benefits," says Sarah Hallberg, Virta's medical director. "And if you're not feeling well, it's probably an indication that you're not doing it right." For Virta, she said, the nutritional regimen is only one part of an overall treatment plan.

Venrock partner Bryan Roberts gave nutritional ketosis a shot after investing in Virta. His rationale for trying it was to provide product development feedback, but he also lost ten pounds after enrolling in the program.

Likewise, Vishal Vasishth, a managing director at Obvious Ventures, took Virta up on its offer to try out the product, which includes health coaching and peer support. "I had a great experience," he said. "And I didn't feel like I was having to make any sacrifices."

Other investors became curious about the diet after meeting Virta Health's CEO Sami Inkinen.

Inkinen was previously a co-founder of online real-estate company Trulia. His journey into health care began when he learned he was at high risk of type 2 diabetes, despite being an endurance athlete.