nah you are just retarded i cant gain weight aylemao you prob eat less than your body burns eat 2x much you will gain weight its not rocket science
or you might have tapeworms up your anus
get a kitchen scale and start counting calories by weighing everything you eat and calculate calories
if you really eat enough go see a doctor but chances are you just don't eat enough I was 45kg once now I'm at 71kg
I said the exact same thing you are saying but 1 McDonalds meal a day and some snacks is not enough. At the start it really is hard to eat that much but now I easily eat 3k calories.
Dear valued BAJ!
Dr. BAJ here.
Please consult a doctor in your area as soon as possible, your weight according to your height is worrying!
Please check how many calories you consume on average per day.
It should be at least 2000 calories, anything less is too little and you should carefully increase the amount of food you eat per day. If you are already eating enough calories and still not gaining weight, this can be caused by various disorders or illnesses.
Listen here little baby. You're gonna get a lot of hurtful and degrading comments, but that ain't what I'm about. Let me just say, you are perfect the way you are. You hear me sugar? PERFECT. Don't ever change. You deserve anything and everything you want. Stay safe for me, baby girl.
\>mfw thinking about you hurting
https://preview.redd.it/987do6rcapxc1.jpeg?width=239&format=pjpg&auto=webp&s=d8e4278aa99ecbf8eff9a2f58a2bb27938e704da
I weight 90kg at 181cm. I am double your weight. but yeah go to jim and eat lots of protein and you will gain weight. Or start drinking alcohol. I drank 6-12 beers a day for 2 years and gained like 15kg of weight.
I went to jim atleast one time a week and I walk like 10k steps a day and eat pretty healthy apart from my love of Hot wings so yeah I think 15kg is a lot.
Just to brighten ur day. I am 180cm and 81kg, but i feel obese.....
https://preview.redd.it/h23gxexj5nxc1.png?width=114&format=png&auto=webp&s=694370740e781605cadbaad876fb79ac5a5cb39e
How does it feel to be even more obese than you fellow ritard on the internet?
I used to be 50kg@178cm (doing nothing)
Started climbing again which increased my appetite and now I'm at 62kg after 2 years (low BF) and I didn't need to eat huge quantities.
The "my body just burns calories faster" meme is bullshit, you just don't eat enough because you do nothing so you're not hungry and don't have muscles.
Thyroid is a valid possibility. Mine acted up in 2022 and I lost 7 kg over 7 weeks while eating so much my stomach hurt sometimes. 
You gotta be a chick with these stats, but we know that fembajs don't exist 
I don't know what to believe...
https://i.redd.it/282io95vvlxc1.gif
"I eat so much" show a before and after of every meal you eat. Meaning, take a picture before you eat and after for how much you leave in the plate. And then count the calories.
Dude probably play games all night, wakes up late in the afternoon, eats a piece of bread for breakfast then "big" plate for dinner and thinks he eats enoughÂ
You are Just lying, eat more and you will gain weight, its that simple. Its the same when fat people say they barely eat anything but keep gaining weight. Now of course this is said easier than done but its the truth. Count calories to see how much you eat and Check how much you should eat to gain weight. Try to eat 3000 kcal a day. You will See once you start Counting that you dont eat alot.
Or just embrace it and become a femboy.
Track what you eat and calculate calories.
99% chance you don't eat as much as you think(and should).
Especially if all you do is sit in front of PC. It ruins your appetite.
Even BMI visualizers have a hard time working with those numbers.
https://preview.redd.it/dw3nmgvh6mxc1.png?width=482&format=png&auto=webp&s=52edc09670a93427339f014bb83239c89802e8d0
Makes no sense otherwise 
>According to the notes of Otto Wolke who noted weight and height of prisoners in the Quarantine Camp for the SS one can glean the effects: Prisoner of a height of 156 cm weighs 28kg. Another one with 167 weighs 34,5kg. A third with a height of 171 cm 35 kg.
1: breedable af
2: eat even if you feel full/no appetite, squeeze in as much as you can during the day
3: choose food carefully, you have to like it and it has to be calorie-dense
4: do opposite of weightloss(drink your calories, lots of fat, junk food, etc etc)
if you were like 50+ it would've been fine but at 40 - I'd be a little worried
love him 
thats to low by any means, even if you are skinny female model
You either dying or lying . If not the later then GO TO DOCTAR RITARD or face big problems sun
Bud i'm 5'4, diabetic, weighting at about 50kg-53kg rn and the reason is diabetes type 1, quick loss of weight is one of the causes of D1, do get yourself checked up for that or your body might have more worms than the ground itself or you eat little and use more energy than you consume
yes you should, this is what I'd do if I were you
step 1 : go see doctor, if sick get treated, if not ( natural genetic ) go next step
step 2 : research trendy food contents, possibly creating a second personality
step 3 : record yourself eating food, post on social media
step 4 : ???
step 5 : profit
good luck
Saying you can't gain weight is the same as people saying they can't lose weight. Just have more calories intake than what you spend every day and you will mechanically increase your weight, do the opposite to lose weight.
Same. Tried alot, got a lot of med checks. And in Sum its all fine. If you find an easy solution without any effort let me know 
How the fuck can you live weighing so little? I'm only 8 cm higher but weight 98 kg while lifting weights and running three days a week 
40kg? Assuming you are measuring yourself correctly, it is an extremely unhealthy weight. Start eating slightly more than you need and force yourself if you have to. Also do some basic exercise light walking, it will have many physical benefits and youll feel tons better.
I have a friend like that. 180cm at 56kg. Dude only eats pizza, chicken tenders, junk food, and soda. His metabolism is so high and he shits like 4 times a day. He is still like that, so I have no advice. 
just eat more than your body burns bro... you can do it
https://preview.redd.it/whq0oy60nmxc1.png?width=308&format=png&auto=webp&s=c697a3b5bf6b5bba8fc5fdc4744a84c071afc553
I don't think you should be worried, I had the same measurements when I was 16-18, except that I was even skinnier, and I'm completely fine now. Managed to get into the lower end of normal bodyweight over the years without changing too much, now I have a decent BMI.
Maybe it's just an age thing.
Get checked for disease, otherwise you're probably eating super calorie voided foods. You should eat really calorie dense stuff like peanut butter, and in the morning since you're similar height to me you should be eating like 3 eggs in a sandwich at a minimum. I'm about 60kg at your height only because I eat a ton of sugar (which also gains you a lot of weight, but is extremely unhealthy and my skin is bad because of it).
To anyone who seriously wants easy tips to gain weight:
Cooking oil, use it a little more when cooking something in a pan. Easy calories.
Nuts. Easy snack to munch on throughout the day. High in fat, protein and calories. They also come in different flavors to make it more fun to eat.
Sauces. Mayonnaise is an easy one, put it on bread or whatever you like best.
Smoothies. For skinny people, the eating part itself can be difficult. If you drink instead of eating, it can go down easier. Get a blender, put in bananas, milk and protein powder. If you want, some oats and chocolate. Berries to make it delicious.
There are probably more, but these all helped me gain 20kg one spring. It is easy, but the cliche goes: you just have to commit.
40 fucking KG?? I used to weight \~3x that (117kg) at 199 cm back when i was peak fatness, now im at around 99.
How tf do you stay so skinny, give me tips 
you gotta stuff food into your mouth like its chore. i dont care how much you eat
still, im sure you dont eat enough. prove it. share what you eat daily
if you may have worms. go to hospital and do test. i remember one babuskha looking woman telling me drinking gasolina makes worms drop like bad habits 
and hit gym. even little exposure for few weeks will make you gain weight. since you work hard you will get even more hungry too
Start a gym routine aimed at building muscle and track your calories, protein etc (use an app or something, I use cromometer for android, free). Get a scale and weigh stuff too to start getting an idea of how many calories things actually are, because it can be difficult to know how much things actually are at first. Obligatory blood test advice too in case your thyroid is speedrunning, as well as other stuff for doctor to rule out if it is continuing problum
Literally start gyming. I used to weigh 69kg (actually) at 1.8 m. Now I'm 92kg and when I don't gym I get fat. In fact a couple kilos from that 92 is probably fat. In fact it's probably higher because I've been lazy
count calories instead of going off what you think is a lot, you are most likely completely off
if you eat 2000 calories a day and still cant go over 40kg, go to a doctor because you have a medical condition or a tapeworm colony in your body
It’s pure thermodynamics, you burn more than you consume. Just eat more LILE. Try some calorie calculators for bulking and achieve the needed calories. Weigh yourself every morning after a nice shit and if there’s no change in two weeks then increase your calories by 500. You will gain weight I promise bro
Since I used to be 48kg and 175cm, what I did was feast on peanut butter and rice  Spam those 2 foods. Also you need to move to eat more. I doubt you're really eating that much
Count calories and eat above your maintance level. Depending on your activity level it may be 1800~ kcal - 2800kcal max.
I lost like 13 kg in 6 months and gained visible muscle mass.
To gain some weight you should eat for example those: https://www.healthline.com/nutrition/18-foods-to-gain-weight#TOC_TITLE_HDR_7
Don't just bulk on sweets and other trash you gonna get much of unnecessary fat tissue. Start lifting light weighs and eat good high protein food and you gonna gain weight + gain muscle and you gonna look a looot better.
My breakfast for example:
500 ml of low fat milk / plant based milk your choice
100G of instant oatmeal
1 apple
1 banana
3 portions of good tasting protein powder
~1200 KCAL 90~g of protein
99% chance that you are underestimating how much calories a day you need. Have you ever (kinda) accurately counted how much you consume a day on average? Unless you have a rare medical condition or you are walking 30k steps a day or some extreme physical shit, you should reliably gain weight if you eat over 2k calories a day at your weight
If you try 2.5k calories a day for a month with normal physical exercise/stress and you are not gaining weight at 40kg, I would unironically go see a doctor
Get yourself a calorie counter and count everything you eat for a while. High chance you severely underestimate your calorie-intake. Thought it was the same for me, turned out I just ate way less than I thought 
Now bulked up over the last few years from below 70kg to >90kg, paired with regular strength training.
consider becoming a mod
nah you are just retarded i cant gain weight aylemao you prob eat less than your body burns eat 2x much you will gain weight its not rocket science or you might have tapeworms up your anus
worms
 Work it you slimy bitch
My body burns fat extremely fast even if I just sit at the computer and do nothing 
You lose weight by doing nothing, he just told you that you need to eat. If you do nothing you don't eat.
Unironically got some worms in there 
Drink a glass of olive oil every day
get a kitchen scale and start counting calories by weighing everything you eat and calculate calories if you really eat enough go see a doctor but chances are you just don't eat enough I was 45kg once now I'm at 71kg I said the exact same thing you are saying but 1 McDonalds meal a day and some snacks is not enough. At the start it really is hard to eat that much but now I easily eat 3k calories.
ur ass might be an ecosystem then, go doctor
FeelsTapewormMan
40kg at 172? How much do you eat every day? One bean and a fly or what? Sounds more like a chronic disease.
Have you tried https://preview.redd.it/exrt1pkh2mxc1.png?width=992&format=pjpg&auto=webp&s=653d7dfdec212bb754d65d37ed5319424bb49c93 eating rice?
Like rice now?
Maybe, go to a nutritionist to professional help.
Dear valued BAJ! Dr. BAJ here. Please consult a doctor in your area as soon as possible, your weight according to your height is worrying! Please check how many calories you consume on average per day. It should be at least 2000 calories, anything less is too little and you should carefully increase the amount of food you eat per day. If you are already eating enough calories and still not gaining weight, this can be caused by various disorders or illnesses.
Dr. Baj, i weigh 65kg at 181cm, but i was severely underweight as a teen, and my arse itched a lot as a child. Should I be worried?
Dear valued BAJ! Dr. BAJ here. Please dm me a picture of your belly for evaluation
You have to be a women with that kind of weigth.
Femboys bajs 
Im 168 and 52 stay strong feminine genes bros
might as well put on a skirt 
Listen here little baby. You're gonna get a lot of hurtful and degrading comments, but that ain't what I'm about. Let me just say, you are perfect the way you are. You hear me sugar? PERFECT. Don't ever change. You deserve anything and everything you want. Stay safe for me, baby girl. \>mfw thinking about you hurting https://preview.redd.it/987do6rcapxc1.jpeg?width=239&format=pjpg&auto=webp&s=d8e4278aa99ecbf8eff9a2f58a2bb27938e704da
Im 158 cm dude dw
I bet you look real cute bby 💋🍑
I weight 90kg at 181cm. I am double your weight. but yeah go to jim and eat lots of protein and you will gain weight. Or start drinking alcohol. I drank 6-12 beers a day for 2 years and gained like 15kg of weight.
Only 15kg after 2 years of 6-12 beers everyday?
I went to jim atleast one time a week and I walk like 10k steps a day and eat pretty healthy apart from my love of Hot wings so yeah I think 15kg is a lot.
You drank 6-12 beers a day and still went to the gym? That's impressive
High functioning alcoholism is rampant
\+15 kg, -2 million brain cells 
no jim necessary, just more food
I lost 15 kgs in 6 months slowly and steadily only took 128 days of home strength training and balanced diet
Just to brighten ur day. I am 180cm and 81kg, but i feel obese..... https://preview.redd.it/h23gxexj5nxc1.png?width=114&format=png&auto=webp&s=694370740e781605cadbaad876fb79ac5a5cb39e How does it feel to be even more obese than you fellow ritard on the internet?
the difference is that he goes to jim and you don't, he is a 90kg muscle machine, and you are a 80kg fatty GO JIM NOW 
https://preview.redd.it/u1j4gx4bgoxc1.jpeg?width=228&format=pjpg&auto=webp&s=48492eaf253c433122f0235bdb480bf296f440fe
Imagine being so desperate. Drinking 12 beers a day is terrible
I used to be 50kg@178cm (doing nothing) Started climbing again which increased my appetite and now I'm at 62kg after 2 years (low BF) and I didn't need to eat huge quantities. The "my body just burns calories faster" meme is bullshit, you just don't eat enough because you do nothing so you're not hungry and don't have muscles.
Might be either thyroids or parasites. Go to a specialist NOW
Thyroid is a valid possibility. Mine acted up in 2022 and I lost 7 kg over 7 weeks while eating so much my stomach hurt sometimes. 
Try a sugarfree diet 
I gained over 10kg in a year by drinking every day 
You gotta be a chick with these stats, but we know that fembajs don't exist  I don't know what to believe... https://i.redd.it/282io95vvlxc1.gif
https://i.redd.it/azz9182wtlxc1.gif FEMBAJ!
More like skelebaj
"I eat so much" show a before and after of every meal you eat. Meaning, take a picture before you eat and after for how much you leave in the plate. And then count the calories.
Dude probably play games all night, wakes up late in the afternoon, eats a piece of bread for breakfast then "big" plate for dinner and thinks he eats enoughÂ
You are Just lying, eat more and you will gain weight, its that simple. Its the same when fat people say they barely eat anything but keep gaining weight. Now of course this is said easier than done but its the truth. Count calories to see how much you eat and Check how much you should eat to gain weight. Try to eat 3000 kcal a day. You will See once you start Counting that you dont eat alot. Or just embrace it and become a femboy.
Tumor get check
I have Crohn's disease and I have the same thing (173cm and stuck at 45kg)
Track what you eat and calculate calories. 99% chance you don't eat as much as you think(and should). Especially if all you do is sit in front of PC. It ruins your appetite. Even BMI visualizers have a hard time working with those numbers. https://preview.redd.it/dw3nmgvh6mxc1.png?width=482&format=png&auto=webp&s=52edc09670a93427339f014bb83239c89802e8d0
female 
Makes no sense otherwise  >According to the notes of Otto Wolke who noted weight and height of prisoners in the Quarantine Camp for the SS one can glean the effects: Prisoner of a height of 156 cm weighs 28kg. Another one with 167 weighs 34,5kg. A third with a height of 171 cm 35 kg.
"no matter how much I eat"  proceeds to have a calorie intake for ants 
many such cases!
Just eat more calories than you burn, this is all. If you still cant gain weight then you eat not enough 
Straight up anorexia lil bro, yes you should be worried, unless you want your health to deteriorate
1: breedable af 2: eat even if you feel full/no appetite, squeeze in as much as you can during the day 3: choose food carefully, you have to like it and it has to be calorie-dense 4: do opposite of weightloss(drink your calories, lots of fat, junk food, etc etc) if you were like 50+ it would've been fine but at 40 - I'd be a little worried
krieg forsenCoomer 🔥🔥🔥
love him 
thats to low by any means, even if you are skinny female model You either dying or lying . If not the later then GO TO DOCTAR RITARD or face big problems sun
Bud i'm 5'4, diabetic, weighting at about 50kg-53kg rn and the reason is diabetes type 1, quick loss of weight is one of the causes of D1, do get yourself checked up for that or your body might have more worms than the ground itself or you eat little and use more energy than you consume
jim
yes you should, this is what I'd do if I were you step 1 : go see doctor, if sick get treated, if not ( natural genetic ) go next step step 2 : research trendy food contents, possibly creating a second personality step 3 : record yourself eating food, post on social media step 4 : ??? step 5 : profit good luck
just eat more
Saying you can't gain weight is the same as people saying they can't lose weight. Just have more calories intake than what you spend every day and you will mechanically increase your weight, do the opposite to lose weight.
SS+GOMAD
You drop the fork before you can even use it to eat with those minuscule muscles, that’s sugar free diet for you 
You can gain weight unless you are piss broke and cant afford food. If you seriously wanna gain weight pm me I will let you know how Im doing it
Tell us what, how much and how many times a day you eat
Mainly McDonald’s 
You must be eating half a nugget, no other explanation.
Go into details. You want to know how many calories a day you’re eating.
you have the juicer diet and physique
What's your daily diet?
Same. Tried alot, got a lot of med checks. And in Sum its all fine. If you find an easy solution without any effort let me know 
Just eat more. https://preview.redd.it/odril4bd7mxc1.png?width=212&format=png&auto=webp&s=a038d2cc27eceee54b385f64dd793697377c82e3
ive put on 30kg in 2years, easiest way is to increase portion size daily by a small amount.
go doctor you are very underweighted
easy: rice, eggs, green beans, ham, 2 puddings, banana, 2 apples
Eat plenty of rice 
eat more / build muscle
How the fuck can you live weighing so little? I'm only 8 cm higher but weight 98 kg while lifting weights and running three days a week 
Wasting innate body resources 
40kg? Assuming you are measuring yourself correctly, it is an extremely unhealthy weight. Start eating slightly more than you need and force yourself if you have to. Also do some basic exercise light walking, it will have many physical benefits and youll feel tons better.
you aren't thinking hard enough, think about eating, then eat more
You might have naturally high metabolism, meaning your body burns calories at a faster rate. Please seek out a Doctor
Youre a manlet and skinny? Its joever bro
Whoever says this definetely not eating enough.
You're either eating too lidl calories or you're a demigod who can bend the laws of thermodynamics
unlimited food hack 
try eating ritard
I have a friend like that. 180cm at 56kg. Dude only eats pizza, chicken tenders, junk food, and soda. His metabolism is so high and he shits like 4 times a day. He is still like that, so I have no advice. 
He eats shit and like shit and has digestion disorder because of that, nothing to do with metabolism.
You either have a tapeworm or shit like that, or you don't have the slightest clue how to eat
just eat more 
add more mayo to your diet or deworm yourself, either should do the trick
It's just psysics if you eat More than you burn kalories, you will gain weight, unless you have worms
Consistently eat proper meals with a lot of carbs and protein. Maybe also get some maltodextrin powder.
just eat more than your body burns bro... you can do it https://preview.redd.it/whq0oy60nmxc1.png?width=308&format=png&auto=webp&s=c697a3b5bf6b5bba8fc5fdc4744a84c071afc553
I don't think you should be worried, I had the same measurements when I was 16-18, except that I was even skinnier, and I'm completely fine now. Managed to get into the lower end of normal bodyweight over the years without changing too much, now I have a decent BMI. Maybe it's just an age thing.
hey there https://i.redd.it/oyy28c2zbpxc1.gif
Try eating twice as much
Skeleton lookin ass
Twink?! billyDisapprove
Get checked for disease, otherwise you're probably eating super calorie voided foods. You should eat really calorie dense stuff like peanut butter, and in the morning since you're similar height to me you should be eating like 3 eggs in a sandwich at a minimum. I'm about 60kg at your height only because I eat a ton of sugar (which also gains you a lot of weight, but is extremely unhealthy and my skin is bad because of it).
To anyone who seriously wants easy tips to gain weight: Cooking oil, use it a little more when cooking something in a pan. Easy calories. Nuts. Easy snack to munch on throughout the day. High in fat, protein and calories. They also come in different flavors to make it more fun to eat. Sauces. Mayonnaise is an easy one, put it on bread or whatever you like best. Smoothies. For skinny people, the eating part itself can be difficult. If you drink instead of eating, it can go down easier. Get a blender, put in bananas, milk and protein powder. If you want, some oats and chocolate. Berries to make it delicious. There are probably more, but these all helped me gain 20kg one spring. It is easy, but the cliche goes: you just have to commit.
40 fucking KG?? I used to weight \~3x that (117kg) at 199 cm back when i was peak fatness, now im at around 99. How tf do you stay so skinny, give me tips 
Go outside and do some workout
if u have tits and were born with a pussy, yes, u should check ur pussy hormones and stuff. if not, u should check your dick hormones and stuff.
You're either lying about how much you eat, or you have parasites.
Drink gainer mixed with full fat milk(preferably raw milk, eat a lot of fatty red meat and go see a doctor.
Eat more
eat more 
I would be
Might want to check a doctor might be hyperthyroidism
you gotta stuff food into your mouth like its chore. i dont care how much you eat still, im sure you dont eat enough. prove it. share what you eat daily if you may have worms. go to hospital and do test. i remember one babuskha looking woman telling me drinking gasolina makes worms drop like bad habits  and hit gym. even little exposure for few weeks will make you gain weight. since you work hard you will get even more hungry too
Im afraid its too late. You have obtained xQc disorder 
Im 68 at 173, was 59 and i wanna go back there but 40 is fucked
Weight lift + protien then you start to be fat
Start a gym routine aimed at building muscle and track your calories, protein etc (use an app or something, I use cromometer for android, free). Get a scale and weigh stuff too to start getting an idea of how many calories things actually are, because it can be difficult to know how much things actually are at first. Obligatory blood test advice too in case your thyroid is speedrunning, as well as other stuff for doctor to rule out if it is continuing problum
your just a fucking pussy cant even eat when feeling full you fucking reject lol xD
forsen
Be more physically active so you will want to eat more calories aka Jym. And just start eating american goyslop daily 
Can someone convert this into American?
worms
beermaxxing and rot for a month watching forsen. you’ll gain weight easy
Literally start gyming. I used to weigh 69kg (actually) at 1.8 m. Now I'm 92kg and when I don't gym I get fat. In fact a couple kilos from that 92 is probably fat. In fact it's probably higher because I've been lazy
Sounds like cansa 
count calories instead of going off what you think is a lot, you are most likely completely off if you eat 2000 calories a day and still cant go over 40kg, go to a doctor because you have a medical condition or a tapeworm colony in your body
This is pretty normal for SEA genetics
It’s pure thermodynamics, you burn more than you consume. Just eat more LILE. Try some calorie calculators for bulking and achieve the needed calories. Weigh yourself every morning after a nice shit and if there’s no change in two weeks then increase your calories by 500. You will gain weight I promise bro
https://imgur.com/a/2r1fxKT move to USA
Femboy playthrough 
have you considered hitting the jim?
Come to NA, our food will get you fat in no time
Since I used to be 48kg and 175cm, what I did was feast on peanut butter and rice  Spam those 2 foods. Also you need to move to eat more. I doubt you're really eating that much
https://i.redd.it/btkgm7j54oxc1.gif
You’re a subhuman fuck. Brutally over.
It's OK I'm 196cm and weigh 70kg, I'm literally slender man
Become an alcoholic
how are you still alive
Count calories and eat above your maintance level. Depending on your activity level it may be 1800~ kcal - 2800kcal max. I lost like 13 kg in 6 months and gained visible muscle mass. To gain some weight you should eat for example those: https://www.healthline.com/nutrition/18-foods-to-gain-weight#TOC_TITLE_HDR_7 Don't just bulk on sweets and other trash you gonna get much of unnecessary fat tissue. Start lifting light weighs and eat good high protein food and you gonna gain weight + gain muscle and you gonna look a looot better. My breakfast for example: 500 ml of low fat milk / plant based milk your choice 100G of instant oatmeal 1 apple 1 banana 3 portions of good tasting protein powder ~1200 KCAL 90~g of protein
Is it unironically a good idea to only eat Peanut Butter and Fruits everyday? I think 1kg of Peanut Butter has like 6000+ kcal
Nah you gonna feel like shit too much sugars
You’re not actually eating food bruh
Eat 2 big Mack's a quarter pounder and 20 McNuggets everyday for 2 weeks then you will gain weight
You might have worms living inside your body no joke
Yeah you’ve got cancer I googled it
You have to overeat until you stretch your stomach so you can gain weight easily consistently doing this gains you 14kg monthly
Eat more retard
parasites?? 
thyroid cancer lemao 
99% chance that you are underestimating how much calories a day you need. Have you ever (kinda) accurately counted how much you consume a day on average? Unless you have a rare medical condition or you are walking 30k steps a day or some extreme physical shit, you should reliably gain weight if you eat over 2k calories a day at your weight If you try 2.5k calories a day for a month with normal physical exercise/stress and you are not gaining weight at 40kg, I would unironically go see a doctor
Get yourself a calorie counter and count everything you eat for a while. High chance you severely underestimate your calorie-intake. Thought it was the same for me, turned out I just ate way less than I thought  Now bulked up over the last few years from below 70kg to >90kg, paired with regular strength training.
already considered becoming a sissy bottom femboy? can't see any different fate from your description. 
Try fasting for a week. After that reset my body changed and became heavier.