Many times in the forums we talk about how to lose hunger, how not to eat so much etc.
But few times in the forums they talk about how to increase hunger and apparently lack of hunger is a more common problem than it seems.
So I will write a guide on how to increase hunger with the protocols that I have used and that several of my friends too.
First of all say that hunger depends on many factors, psychological, nutritional, sports, health, the type of chemistry we are using, supplements ... So I will talk about all these issues.
Also say that if you feel hungry but you fill up very quickly this guide is also for you.
BTW: This guide also discusses how to improve intestinal health.

Phsycology
Your feelings and problems can be the triggers of not being hungry, stress situations increase adrenaline eliminating appetite completely.
A depressive mood can cause a lack of hunger that will increase in time.
In this section I can only give one piece of advice and it is: fix your life, the problems and toxic situations you have will have to disappear for your sake, trust your family, friends or a professional such as a psychologist.
In my opinion, medications to eliminate stress or depression are pure poison,those are very addictive and they do not solve anything, it is like putting a band aid in a gunshot wound, in the short term it can be used to stop the bleeding, but in the long term If you don't get the bullet, you're going to bleed to death.
The only thing that could be helpful is to practice breathing exercises at the speed that marks a Gif based on Bainbridge Reflex (you can search on Google) 15 to 20 minutes before meals.

Diet
The diet is key in the bodybuilding world, and one of the main causes of the loss of hunger, I explain, the stomach is like (and some parts are) a muscle, with each meal we train it, if we train very often or with a lot of intensity or with a lot of weight we end up tired and not wanting to continue training, because with the stomach it happens exactly the same.
My first advice would be to space meals as much as possible to digest food.
The second tip would be to eat fast (chewing, but fast), I explain myself: as soon as we start eating our body stops releasing ghrelin and begins to release leptin so our hunger disappears the longer the food lengthens regardless of what we are eating.
My third and most important advice, to make a diet low in FODMAP (you can find on the Internet how to do it and believe me it is very effective).
https://www.ncbi.nlm.nih.gov/pubmed/29763907

Exercise

I don't need to say much about training, it's simple, the more you train, the more nutrients your body will ask for and this will cause an increase in hunger.
I would recommend training as many times as we consider appropriate for our body and goals and performing fasting cardio (on days with less hunger I relized it and it made me want to eat incredible).

PEDS
Boldenone:
This is my favorite steroid to increase hunger, a continuous hunger that in my opinion is increased as you spend more weeks using it and more frequently weekly injections (increasing the dose from 600mg in my opinion and in my group does not increase significantly hunger).

MK677:
It is a mimetic of ghrelin ... which is the hunger hormone, the bad thing about using this compound to increase hunger is that hunger appears at unexpected times either just after eating or at midnight therefore it is quite uncomfortable .
Also as a general rule after a few weeks hunger usually disappears so it is no longer useful.

GH:
It influences ghrelin in a way (like ghrelin in GH as well).
Hunger increases throughout the day, although there are times when hunger comes in pulses.
Unlike with the MK677 hunger does not disappear soon after using it.

Dianabol:
For some people like me hunger increases and for others it eliminates it, so it was worth noting.

Peptides:
There are many peptides on the market (GHRP, CJC ... etc) that try to increase the release of growth hormone or mimic its pulses and therefore there is also a stimulation in Ghrelin, they are effective: Yes (if you are really buying those products and not some cheap imitation).

The use of oral steroids can cause you to stop being hungry, either because of a liver toxicity that is a direct cause of poor appetite or because of the general toxicity that they cause in the body can cause hunger to disappear (I would not recommend using SD, M1T, Oral tren, Anadrol ... to name a few).

Supplements
For me this is the most important part, I will explain only the supplements I used to improve my hunger and intestinal health jointly recommended by my doctor and my dietitian.

Glutamine:
For me the most important supplement of all, has many studies that prove its effectiveness.
https://www.ncbi.nlm.nih.gov/pubmed/30108163

The protocol I used was the following:

First week: 30 grams twice a day.
Second week: 20 grams twice a day.
Third and following weeks: 10 grams twice a day.

Berberine:
It modulates the response of TNF-a in the intestine and increases the AKT and improves the transport of glutamine through the intestine

Probiotics:
There are many probiotics that without intestinal tests can not know which ones are right for you, just ask your doctor for a test and he will recommend it based on it.

Vitamin A:
Necessary for proper instestinal functioning.

Pharmacology

This part is only to be used if the rest of the sections have not served you, the following medications would have to be prescribed by a doctor (as it was in my case and that of one of my colleagues). It should be said that these substances cannot cause overdose or serious health problems such as a certain substance that is taboo in the forum (and that I have also seen applied in hunger augmentation protocols which I would never recommend when there are much simpler and less dangerous ways) .

Megestrol acetate
This medicine is indicated to increase appetite in people who are in treatment against cancer or severe anorexia.
It is the most potent and effective medicine on the list ... and perhaps one of the ones I like the least because of its mechanism of action and excessive power.

First generation antihistamines.
All cause hunger to a greater or lesser extent and can be prescribed by the doctor to increase your hunger. (They have many side effects among which the dream stands out).

My complete intestinal health protocol:

First step: remove.

Eliminate all foods that cause gastrointestinal discomfort, we can find out what they are through a diet low in FODMAPs.

Second step: Repair.
This would be when we would use the following Glutamine protocol:
First week: 30 grams twice a day.
Second week: 20 grams twice a day.
Third and following weeks: 10 grams twice a day.
In addition to Nac 1500mg per day and ALA at 500mg per day.

Third step: Repopulate.
Now is the time to use probiotics and prebiotics, the best probiotics in my opinion would contain acidophilic lactobacilli and bifidobacterium bifidum.

Fourth step: Improve.
Add fermented foods (such as Kefir or Kimchi) and add digestive enzymes.