Support during weight loss journey

My (f, early 30s) husband (m, early 30s, BMI of 39) started his weight loss journey recently. He has been overweight our entire relationship (6 years). Now that we are expecting, he wants to take care of his health and lose weight with a weight loss program by the local hospital. I really appreciate that. As someone who has never been overweight I would appreciate your thoughts and ideas how I can support him best. Thank you!