This is ridiculous and naïve and applies the stick where the carrot would be more effective.
I was homeless for a few years when I was a teenager and meal deals were a life saver. Often a meal deal has been my only food for the day. People living on an extremely limited income need to buy things that are low cost/high calorie.
And no one is fat because of meal deals, they're fat because of emotional eating, binge eating, relying on takeaways and ready meals due to lack of time/energy, and sometimes lack of access to cooking facilities, or lack of knowledge about cooking and nutrition.
I have plenty of money now, and what do you know, now I can afford to shop in M&S and Waitrose there are tons of healthy pre-prepared food options that simply weren't available to me when I was homeless. There's so much judgement and classicism wrapped up in food. Someone eating a Waitrose pre-prepared kumquat and puy lentil salad is going to be perceived and judged very differently than someone stuffing a Tesco triple cheese sarnie in their gob; Mumsnetters certainly respond very differently to the idea of a Charlie Bigham fish pie than an Asda frozen chicken tikka masala. Not because of health but because of perceptions of money and class.
Restaurant food is usually crazy high in fat, calories, salt and sugar, yet (with the exception of fast food places/chains) restaurants are rarely criticised or targeted within the obesity debate. Again, it's about money/class, not health.
If supermarkets and other places sold a wider range of cheap and convenient healthy food then people would eat it. Factories don't need to stuff as much fat, salt and sugar into their food as they do, they do it to maximise profit. It would be extremely easy for food manufacturers to make healthier pre-packaged foods, they just don't want to - the government should penalise them, not the general public, but they won't because food lobbies are too powerful and donate too much money to the government.
Whenever the issue of the link between poverty and obesity is raised there's always people sneering and saying "oh the poors should just learn to cook lentils!" Plenty of people living in poverty don't have access to cooking facilities. Either because they just don't have access to a kitchen at all (I certainly didn't have access to a kitchen when I was younger) or because they can't afford fuel costs. If we're talking specifically about lunch, very few people other than SAHM, unemployed/students, and people in cushy WFH jobs are at home and have enough free time to make a cooked lunch in the middle of the day. And before people start talking about just cooking lunch the night before, it's not really practical or pleasant to have to cart a packed lunch around on public transport all day then eat something that's been squished at the bottom of your bag for hours.