A key factor of Nudge Theory is basically the ability for an individual to maintain freedom of choice and to feel in control of decision making on their own.
According to Nudge theory, encouraging positive choices rather than punishing undesirable behaviour is more effective in changing people's behaviour. A nudge is when fruit is placed at eye level.
For more information you can see the attached link
Depends of course, this handbook has a good critical overview across the social sciences, and therein, the chapter on nudging and the politics of health might be of interest particularly by Muireann Quigley and Anne-Maree Farrell : https://www.elgaronline.com/view/edcoll/9781785367847/9781785367847.00021.xml (If you want more critical approaches on the politics of nudging and behavior change in general, happy to send you more info)
In Richard Thaler’s book ‘Nudging & Behavioural Economics’, he popularised the nudge theory. It reveals ways to influence behaviour and decisions made by groups and individuals. An individual is more likely to decide something when nudged simply by altering the environment so that automatic cognitive processes are triggered to favour the desired outcome.