Ultimately, money is the only thing that can keep a startup going. That means either sales and revenue or investment, and getting investment is a lot easier if you have sales and revenue.
Eating more healthily, getting more sleep, and doing some exercise are useful for staying focused and selling better, but the number of successful startups whose founders had horribly unhealthy lifestyles yet still managed to sell their product is significantly higher than the number of startups with healthy founders who didn't sell anything.