In many ways, Kimbal Musk shares his brother Elon Musk's determination to improve humanity. Elon, 45, is the CEO of tech giants Tesla and SpaceX. He is pioneering zero-emission travel and working towards colonizing Mars. Kimbal, 44, is the founder of casual dining upstart The Kitchen, and he is working to improve nutrition by expanding healthy and affordable dining options across the country. "[My brother] told me it was crazy to get into the food business; I told him it was crazy to get into the space business," Kimbal jokes. "It's working out fine." The less-public Musk brother, who sits on the boards of Tesla and Chipotle, has quietly been scaling his passion project with two concepts: His high-end restaurant The Kitchen, based in Boulder, Colo., and his chain Next Door, made up of affordable farm-to-table restaurants. In January, he announced plans to bring well priced, locally sourced options to America's heartland by opening 50 new restaurants by 2020.

Kimbal Musk meets with Square Root farmers at the company's Brooklyn headquarters, home to farms housed in shipping containers. Mary Stevens | CNBC

Similar to Chipotle's strategy of providing cheaper, healthier options by sourcing and scaling quality providers, Musk uses his two restaurant concepts to help control costs. His favorite example is sourcing whole cows from local farmers in Colorado. "We buy the whole cow, and we're able to do the prime cuts [that] go to The Kitchen; the burger will go to Next Door," he says. "To get a naturally raised cow of that quality and to serve [a burger] for $8.95 is an extraordinarily low price." The Kitchen's non-profit arm has also installed nearly 350 Learning Gardens in schools across the country to teach kids about nutrition and the importance of eating healthily. "I've always loved food, but I've started to understand the problem more and more," Musk says. "Industrial food has totally failed America … and so the more I dig in, the more I get passionate about being part of solving that."

Industrial food has totally failed America ... I get passionate about being part of solving that. Kimbal Musk founder of The Kitchen

Indeed, Americans are facing a number of nutritional issues. More than a third of the country's population is considered obese, while less than a quarter eat the recommended daily servings of fruits and vegetables, according to the Centers for Disease Control and Prevention. And being short on time or money can often lead families to settle for less nourishing options — a reality Musk is determined to change. "It's not as hard as people think. It's just that people have lost the skill of cooking," he says, adding that he keeps his own grocery budget low to understand what the average family can afford. He's also empathetic when it comes to time constraints. But despite his busy schedule, "we always make a point of sitting down with the family even if I have other work to do," he says.

Kimbal Musk gives investors a tour of Square Roots, a Brooklyn urban farming start-up he cofounded. Mary Stevens | CNBC

Unlike his brother's college experiment of eating hot dogs and oranges to prove he could survive on $1 a day, the younger Musk makes a point to eat whole, nutritious foods that don't break the budget. Here's a look at what he typically eats: Breakfast: Two Eggs and a piece of toast

"I think eggs are one of the greatest gifts to the Earth, and it gives me the energy and nutrition to go through [my day]." Lunch: Greek salad and meatballs "It's phenomenal. The Greek salad is a classic. It never goes away and you can do that really affordably."

A Greek salad from his Next Door restaurant. Next Door |

Dinner: Roasted chicken and vegetables "I'll have dinner at 6:30 with the kids and then get back to work after that if I need to. My favorite thing to do is roasting a chicken. I can get home at 5:00. I can have dinner ready on the table with a fully roasted chicken by 6:30. "I can do a whole roast chicken with two sides of vegetables for a total cost of $10," he says. "You can easily feed a family of four with a chicken. It's just skills we've lost, not that it's not affordable — it's very affordable."