What is the ruling on an able-bodied adult man who does not fast? What is his punishment in this world?

Praise
be to Allah

Fasting Ramadan is one of the pillars of Islam, and it is not
permissible for an adult Muslim of sound mind who is accountable to break
the fast in Ramadan except with an excuse, such as travelling, sickness and
the like. Whoever breaks the fast – even for one day – with no excuse has
committed a major sin and has exposed himself to the wrath and punishment of
Allah. He must repent sincerely and make up the days that he did not fast,
according to the majority of scholars; some of them narrated that there was
consensus on this point.

Please see question no. 234125 

As for the one who deliberately does not fast in Ramadan,
thinking it permissible to do so, he has become a disbeliever. He should be
asked to repent, and if he repents, all well and good, otherwise he is to be
executed.

Whoever openly breaks the fast should be given a disciplinary
punishment by the ruler, a punishment that will deter him and others like
him from doing this grave act.

There follow a number of comments by the scholars concerning
that.

Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him)
said:

If a person breaks the fast in Ramadan, believing that to be
permissible although he is aware of the prohibition on doing so, but he
thinks that it is permissible for him, he must be executed. 

If he is an evildoer, he should be punished for breaking the
fast of Ramadan, as the ruler sees fit. 

If he is ignorant, he is to be taught the ruling. 

End quote from al-Fataawa al-Kubra (2/473) 

Ibn Hajar al-Haytami (may Allah have mercy on him) said: 

Major sins no. 140 and 141: Not fasting one of the days of
Ramadan, and breaking the fast by having intercourse or otherwise, with no
excuse such as sickness or travelling. 

End quote from az-Zawaajir (1/323). 

The scholars of the Standing Committee for Issuing Fatwas
said: 

Breaking the fast during the day in Ramadan on the part of
one who is accountable is a major sin, if it is done without a legitimate
excuse. 

End quote from Fataawa al-Lajnah ad-Daa’imah
(10/357). 

Shaykh Ibn Baaz said: 

Whoever breaks the fast on any day in Ramadan, with no
legitimate excuse, has committed a grave evil. Whoever repents, Allah will
accept his repentance, so he must repent to Allah sincerely, by regretting
what he has done in the past and resolving not to repeat it, and he should
ask his Lord for forgiveness a great deal, and hasten to make up the day
that he did not fast.

End quote. 

Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was asked
about the ruling on breaking the fast during the day in Ramadan with no
excuse. 

He replied: 

Breaking the fast during the day in Ramadan with no excuse is
a major sin, and the individual becomes an evildoer thereby. He must repent
to Allah and make up the day that he did not fast. 

End quote from Majmoo‘ Fataawa wa Rasaa’il al’Uthaymeen
(19/89).

An-Nasaa’i narrated in al-Kubra (3273) that Abu
Umaamah said: I heard the Messenger of Allah (blessings and peace of Allah
be upon him) say: Whilst I was sleeping, two men came to me and took hold of
my arms… And he quoted the hadith, in which he said: Then they set off with
me, and I saw some people hung up by their Achilles tendon, with the corners
of their mouths torn and dripping with blood. I said: Who are these? He
said: These are the people who used to break the fast before it was
permissible to do so. 

Al-Albaani classed it as saheeh in as-Saheehah (3951),
after which he said: 

This is the punishment of those who fasted then broke the
fast before the time for breaking the fast came. So how about those who did
not fast at all?! We ask Allah to keep us safe and sound in this world and
the hereafter. End quote. 

For more information, please see the answer to question no.
38747

And Allah knows best.