We all know there is no such thing as a free lunch: so how would things be different if everyone in the world was magically provided a 600 Calorie, regionally appropriate, free lunch every day?
If the food is magically sourced, agriculture will be massively affected as there will be a fourth less demand. There will be less work to go around and people will flock to cities.
However if the food is transported magically from the farms, farmers are going to need to industrialise to keep up with demand.
Economically, people will be better off having to spend less money on food, they can afford luxury goods so that will have a positive impact on merchants initially but then prices will go up (supply/demand/inflation)
In addition, with having to earn less, people will be able to follow their hobbies so expect a bit outpouring of art and maybe even education (see the Renaissance for evidence)
For the very well off this will probably have little-to-no effect.
A free lunch could be convenient but if you're in a mood for something different that day you'll probably throw it away to buy something you really want to eat. Easy come, easy go.
For the not-so-well off this would be a godsend.
Even in first-world countries, the working-poor may sometimes have food security issues, which these free lunches would greatly alleviate. (Reduced-cost school lunches are often suggested by American educators as one method to help combat performance disparity between children from wealthy households and children from poorer households.)
This is only more pronounced in countries/regions where food scarcity is a significant problem. Countries facing drought or famine are magically finding some level of relief. Places living hand-to-mouth by subsistence farming are suddenly able to spend 1/3 of their time on other activities (education, leisure, etc.) or are finally able to save and invest with the 1/3 of their harvest that would otherwise need to be eaten for survival.
The general understanding of the phrase "There's no such thing as a free lunch" is that when the costs are not transparent or hidden from the consumer, then undesirable consequences arise.
The first and most commonly cited is the moral hazard argument. People who are relying on "Free Lunch" at someone else expense will be less inclined to work. This is demonstrated in multiple settings, when jurisdictions relax the requirements for welfare or similar payment mechanisms, the number of people who receive welfare tend to grow, while when requirements are tightened up, the number of recipients shrink. This was demonstrated in Ontario, Canada back in the 1990's when the Harris government tightened welfare, the number of cases dropped dramatically as people denied free lunch returned to the workforce. This also happened in the 1990's under the Clinton Administration's welfare reforms as well, so this isn't a partisan argument. And of course various US States have also reduced welfare cases by instituting work requirements
The second consequence might be called the "all you can eat buffet" effect. In the United States, this is best demonstrated by Medicare/Medicaide. Since people have no idea of the costs of medical procedures now, they tend to demand more procedures and more visits to the doctor. In Canada, under a single payer system, the government attempts to solve this by rationing healthcare, yet the costs continues to escalate since demand outstrips supply by a large margin.
The third consequence of free lunch is people try to game the system. Once again the best known example is the Food Stamp program, where people will buy items and then resell them for cash, in order to purchase things that are not covered. More examples are here
And of course the free lunch has to be paid for somehow. Since the OP never specified how this was to be done, we can go from truly horrific scenarios (people are enslaved to grow the food and prepare the free lunches) to improbable tweaks to the laws of thermodynamics (free lunches magically appear, but an equivalent amount of energy is removed from the Universe as a whole). Regardless, the lunch still is being paid for, just offstage somewhere.