"a square meal"

[Odessa Dawn]

"Authorities around the country are coming under pressure from teachers’ leaders to combat the effects of rising poverty by making sure children start the day with a square meal."
"In Blackpool, one school, Devonshire primary, saw all its 500 pupils take advantage of the offer of a breakfast including fruit, yoghurt, toast, bagels, cereal bars and juice followed by free milk at morning break time."
"Mr Johnson said: “A nutritious breakfast is the best way to prepare our kids for a day of school."
More: More schools providing free breakfasts for pupils to avoid them being unable to concentrate in class

Junk food: food that is low in nutritional value, often highly processed or ready-prepared,…
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More: Junk food | Define Junk food at Dictionary.com

1. junk food
(food that tastes good but is high in calories having little nutritional value)
Definition of junk food

1. fast food
(inexpensive food (hamburgers or chicken or milkshakes) prepared and served quickly)
Definition of fast food

"You really want to stay away from refined and processed foods, things that are found in boxes and packages, certainly sugary foods," she said.
More: Busting a Gut: Keys to Burning Dangerous Belly Fat - Health & Science

The definition of "a square meal" is very clear from the piece itself. But I need a suitable antonym for a square/filling meal, will you help me please? Are fast food, junk food, and processed food antonyms for a square meal?

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Thank you,

 

[JMurray]

Are fast food, junk food, and processed food antonyms for a square meal?

A "square meal" suggests a satisfying quantity as well as quality. In a sense "junk food" and "healthy food" are opposites, but even the healthiest carrot or apple does not normally constitute a "square meal" in itself. Some reasonably nutritious fast food could be a square meal in the way that a single carrot is not.
I don't think there are many antonyms for "square meal", but a "meagre" (US "meager") meal would come close.

not a teacher