Jason Fung is Canadian nephrologist. He's been working with obese and type 2 diabetes patients for years. He's been advocating fasting and time-restricted eating for years to fight obesity and diabetes. He's mostly known for this book "The Obesity Code" in which he details how modern eating habits are wrong and the main cause for the obesity epidemic.

I hope I summed it up well. You might want to look him up on Youtube, he has some really interesting talks.

Google tells me he appears to be a doctor, who specializes in renal diseases (nephrologist), has written several books on fasting, advocates fasting for some patients, and runs something called the Intensive Dietary Management program.