Firstly: 

Extravagance is blameworthy in eating and other things. Allah says (interpretation of the meaning): 

“And eat and drink but waste not by extravagance, certainly He (Allâh) likes not Al-Musrifûn (those who waste by extravagance)”

[al-A‘raaf 7:31] 

“And waste not by extravagance. Verily, He likes not Al-Musrifûn (those who waste by extravagance)”

[al-An‘aam 6:141] 

“And let not your hand be tied (like a miser) to your neck, nor stretch it forth to its utmost reach (like a spendthrift), so that you become blameworthy and in severe poverty”

[al-Isra’ 17:29] 

“And give to the kinsman his due and to the Miskîn (poor) and to the wayfarer. But spend not wastefully (your wealth) in the manner of a spendthrift .

Verily, spendthrifts are brothers of the Shayatîn (devils), and the Shaitân (Satan) is ever ungrateful to his Lord”

[al-Isra’ 17:26-27]. 

The difference between extravagance and wasteful spending is that extravagance means spending on something appropriate in an excessive manner, whereas wasteful spending means spending on something that is not appropriate. This was stated by al-Manaawi in Fayd al-Qadeer, 1/50

Secondly: 

Extravagance leads overstepping the mark, which means eating beyond the point of fullness. This is not limited to one or two or three meals a day. A person may eat one meal a day and eat extravagantly during that meal. Or he may eat three meals without being extravagant. 

The hadeeth of al-Miqdaad encourages eating small amounts of food and being content with that which is enough to keep one going. It does not suggest the number of meals. These few mouthfuls may be eaten at three times, at breakfast, lunch and dinner, and he will be eating little in these meals. If he wants to eat more than a few mouthfuls – in his meal – he should leave one third (of his stomach) for his food, one third for his drink, and one third for air. If he needs another meal – as is the case for most people – there is nothing wrong with that, but he should pay attention to the same points noted above. The same applies if he needs to have three or four meals. The number of meals varies from one person to another, the type of food and the effort necessary to prepare it. 

What matters is taking care of the body and not causing any harm, whether by overeating or starving. 

What also matters is eating to have strength to carry out acts of worship, which is achieved by eating moderate amounts, not by eating heavy amounts or going too hungry. 

It says in al-Mawsoo‘ah al-Fiqhiyyah (25/332): Part of the etiquette of eating is to be moderate in eating and not to fill the stomach. The most that is acceptable in this regard is for the Muslim to divide his stomach into three parts: one third for food, one third for drink and one third for air, because of the hadeeth: “The son of Adam does not fill any vessel worse than his stomach. It is enough for the son of Adam to eat a few mouthfuls to keep him going, but if he must (fill his stomach), then one third for his food, one third for his drink and one third for air.” That will lead to a lean and light body, because eating one’s full leads to heaviness, which makes one too lazy to do acts of worship and strive. When we say one third of the stomach, it means limiting oneself to one third of what one would have to eat one’s fill, and it was said that this may be done by limiting it to one half of a mudd. But al-Nafraawi favoured the former view, because of differences among people. All of this applies to one who will not become weak as a result of eating less than his fill, otherwise it is better for him to eat that which will give him energy to worship and will be physically appropriate for him. 

In al-Fataawa al-Hindiyyah it says: Eating falls into different categories: 

Obligatory – which is that which will ward off death. If a person stops eating and drinking until he dies, then he has committed a sin.

That which is rewarded – which is what will give him more energy so that he is able to pray standing up and makes it easy for him to fast.

Permissible – which is more than that, to the point of eating one’s fill, so that he will have more physical strength. There is no reward for this and it is not regarded as sinful. He will be brought to account for it but the reckoning will be light if the food was halaal.

Haraam – this refers to eating more than one’s fill unless the intention is to have the strength to fast the following day or so as not to embarrass a guest, in which case there is nothing wrong with eating more than one’s fill. 

Ibn al-Haaj said: Eating in and of itself falls into different categories: obligatory, recommended, permissible, disliked and forbidden.

That which is obligatory is that which will keep him going so that he can fulfil his obligatory duties towards his Lord, because that which is essential to doing something obligatory is also obligatory.

That which is recommended is that which will help him to do naafil acts of worship, acquire knowledge and do other acts of obedience.

That which is permissible is that which enables one to fill one’s stomach in the manner prescribed in sharee‘ah.

That which is disliked is that which is a little more than is enough to fill the stomach but does not harm one.

That which is forbidden is eating a great deal that is harmful to the body. 

Al-Nawawi said: It is makrooh to eat more halaal food than is enough to satisfy one. 

The Hanbalis said: It is permissible to eat a great deal so long as it does not harm one. In al-Ghuniyah it says: It is makrooh when there is the fear of indigestion. It was narrated from Ibn Taymiyah that it is makrooh to eat that which leads to indigestion; it was also narrated from him that doing this is haraam. End quote. 

Thirdly: 

From the above it is clear that there is nothing wrong with eating more than one meal a day and that that on its own is not regarded as extravagance; rather extravagance is eating more than is enough to fill one’s stomach even if that is in one meal. 

Among the evidence that it is permissible to eat enough to fill one’s stomch and that what is makrooh or haraam is going beyond that limit is the report narrated by al-Bukhaari (5381) and Muslim (2040) from Anas ibn Maalik (may Allah be pleased with him) who said: Abu Talhah said to Umm Sulaym: I have heard the voice of the Messenger of Allaah (blessings and peace of Allah be upon him) sounding weak, and I know that he is hungry. Do you have anything? … This is a story of food being increased in quantity by virtue of the supplication of the Prophet (blessings and peace of Allah be upon him), in which he said: “Give permission for ten to enter.” He gave them permission and they ate until they were full, then they left. Then he said: “Give permission for ten to enter.” He gave them permission and they ate until they were full, then they left. Then he said: “Give permission for ten to enter.” He gave them permission and they ate until they were full, then they left. Then he gave permission to ten more to enter, and all the people ate, and ate their fill, and there were eighty men. 

Al-Bukhaari included this report in a chapter of his Saheeh entitled: Chapter on one who eats his fill. 

In this chapter he also narrated that ‘Aa’ishah (may Allah be pleased with her) said: The Prophet (blessings and peace of Allah be upon him) died when we had eaten our fill of the two black ones: dates and water. 

Al-Haafiz Ibn Hajar (may Allah have mercy on him) said: Ibn Battaal said: From these hadeeths we see that it is permissible to eat one’s fill, although not doing so sometimes is preferable. … al-Tabari said: But eating one’s fill, even though it is permissible, has its limits, and anything beyond that is extravagance. That which is permissible of it is that which helps the eater to obey his Lord and it is heaviness does not distract him from doing what is enjoined upon him. al-Qurtubi said in al-Mufhim, after mentioning the story of Abu’l-Haytham, when he slaughtered a sheep for the Prophet (blessings and peace of Allah be upon him) and his two Companions and they ate until they were full: In (this report) there is evidence that it is permissible to eat one’s fill, and the reports which say that it is not allowed are to be understood as referring to fullness that weighs heavily in the stomach and makes a person slow to do acts of worship, and leads to feeling sleepy and lazy. The prohibition on doing that (which is makrooh) may go so far as being haraam according to the negative consequences that result from it.

End quote from Fath al-Baari. 

Fourthly: 

The way you described your breakfast, lunch and dinner is not regarded as extravagance; rather they may be small, compared to what people are used to. But you know yourself best and what is best suited to your body’s needs. 

And Allah knows best.