Natural Balance Foods is expanding its Nakd brand with Protein Crunch bars designed to slowly release energy.

The four bars - apple, banana, strawberry and cocoa - have no added sugars or syrups and contain fruit, nuts and 5.5g (18%) of added protein, which the supplier said would help consumers feel fuller for longer.

They roll out to Waitrose and Tesco this month, and to Sainsbury’s from May (rsp: 75p/single bar and £2.29/four-pack).