Staying in bed for a long time and eating more nutrients will make you fat. I think you need to adjust your diet. Avoid food rich in bone soup, sugar and fat, and eat more as usual. Increase milk, fresh fish and shrimp and other foods rich in protein.
Muscles with broken thighs tend to atrophy. Three days after operation, you can do targeted rehabilitation exercises, and you should take the initiative to do strength and endurance exercises after the wound is closed. Exercise should be gradual. Now, if you can't lift your legs, you can also tighten your muscles and use your hands to help move your knees. Exercise three or four times a day for half an hour.