"Super-sized" chocolate bars are to be banished from hospital shops, canteens and vending machines, NHS (National Health Service) England says.
Sweets and chocolate sold in hospitals should be 250 calories or under, the head of the body says.
Under the plans, most "grab bags" will be banned - with hospitals given a cash boost for facilitating the change.
The proposals would also see 75% of pre-packed sandwiches coming in at under 400 calories.
Pre-packed savoury meals and sandwiches must also contain no more than 5g of saturated fat per 100g.
In April, NHS England said it would ban sugary drinks if hospital outlets did not cut down on the number they sell.
Mr Stevens said the NHS was "stepping up" to combat an issue that was causing "an epidemic of obesity, preventable diabetes, tooth decay, heart disease and cancer".
"In place of calorie-laden, sugary snacks we want to make healthier food an easy option for hospital staff, patients and visitors."
NHS staffs are also being targeted as part of the move to tackle unhealthy eating, including those on overnight shifts.
Public Health England says hospitals have an "important role" in addressing obesity and not just dealing with the consequences.