Men who naturally are/were skinny, what are tips to gain healthy weight?

Count calories. Back in my twig days, I always thought "I'm eating so much" but when it came down to actually counting them, i was way overestimating how much I was taking in.

Whole milk and cereal to start the day was a good jumpstart for me

Was never a naturally skinny guy, but invested in my health about 10 years ago by going to the gym and eating better.

Some people will tell him to "dirty bulk", which is basically eat whatever he wants, whenever he wants, and a lot of it. He can also "lean bulk", which seems to be what you're doing, with a surplus of calories.

In short, whichever route y'all decide to go, the goal is to eat at a SURPLUS. If he's usually full from one chicken breast, maybe trying 2 breasts in a sitting OR having him eat at least 2 a day in total whether that's for lunch and dinner or whatever he feels comfortable with. Easy cheat code is extra virgin olive oil when you're cooking.

You're doing everything right! The encouragement and the reassurance is extremely helpful. You just have to continue reiterating to him that eating one meal a day is not enough unless it's a TON of food in one sitting. He has to, to an extent, force himself to eat.

Eat more and lift progressively heavier weights. The latter is important so he doesn't just get skinny-fat (yes, that's a thing for guys).

He needs to eat, whole foods is best.

My advice in steps:

1. Weigh at beginning of week
2. track everything consumed in a week WITH calories (very important - use google, it doesnt need to be 100% on the dot).
3. Weigh at end of week
4. Note the change in weight.
5. Establish a baseline BMR
6. Eat sufficient calories over that BMR - 3500 is a pound gained or a pound lost.
   

I found it helpful to continue tracking calories; later, he can worry about macros and the gym. I'd shoot for 4 pounds a month for healthy gain.

5'8 formerly 115lbs during my teens to early 20s, now ~148lb at 29.

Your BF just needs to have a very serious self reflection about his eating habits. His body is used to maintaining itself at 135, and trying to eat more is going to feel very unnatural to him. I'm going to guess he doesn't eat at least 2 full meals a day.

Calories in > calories out is a very gross oversimplification of it, but in the end that's what matters most. You can try getting him to hit the gym, he doesn't need to necessarily go crazy and chase some big muscles, but pretty much anything he does there will get him hungrier for more calories than he burns there.

Not sure if mentioned already, but might want to check his thyroid hormone levels. If too high can make it difficult to gain weight.

Been trying to crack this code for a looooong time. 5'11" @ 140-145 here. I can never go over...

Start with fixing ONE meal to be more calories - breakfast is usually the one that skinny people fail on. Figure out a good preparation for eggs, try with cheddar mixed in scramble and some cholula. Cottage cheese and some jam can be good, Greek Yogurt, and leftovers of bigger dinners.

Buy the book Starting Strength. Join a gym. Do what the book says. It's a beginner weightlifting book, it will teach him everything he needs for the first 6-12 months when he grows beyond it.

Eat more food, too. Forget the protein shakes right now, he's not big enough to need that. Just stick to whole foods.

I was 125 lbs and 6 ft tall until I was 28 and met my wife.

He needs to eat until he feels like he’s about to throw up, and then he needs a little more. His stomach is likely small due to consistently eating small portions and needs to stretch. At one point my wife sat on my lap and force fed me ice cream.

I am now a healthy and fit 165 at 36 yo

Meal Prep Pro is an excellent app to attack this issue. On it now and eating healthy with calorie surplus for a bulk.

I went from 130 pounds at 6"2' to about 180 pounds and I just ate more of what I already ate and worked out semi regularly (1-3 times per week most weeks). The only thing is to be patient and, as cliché as it sounds, to make it a lifestyle change. It seems the only way to stick to it for long enough.

Eat More substantial meals, sleep more.

There's no secret.

Juices breads beans meat vegetables fruits eggs dairy dessert.

muscle would probably be the best type. but you also have to remember there are different body types... he might just be an ectomorph and everything is functioning normally.

Counting calories helps because he may think he's eating alot and it only ends up equalling like 2000 calories when the goal is let's say 2600.

I find smoothies are a great way to get calories in and it's easy compared to eating. Just look up some weight gaining smoothies.

Working out will help him build up a bigger appetite as well.

I used to weigh 150lbs I'm 6'1. When I first started working the work was so intense for me. My stepmother would cook every night and I ate like a horse. I gained 30 lbs of muscle in 6 months and have maintained the same weight since. So I guess my advice would be to lift weights to the point to where your muscles give out, and eat more.

I’ve always been fairly lean and wanted to bulk as well. Over the last 6 months I gained 30 lbs eating eggs and sausage for breakfast, a protein shake for lunch but I would add fruit, peanut butter, oatmeal, banana, honey for the extra calories/carbs/fat, a steak for dinner with a sweet potato and of course consistent exercise with a basic protein shake after working out. Some snacks in between and an extra meal on occasion if I could.

Simple meals but all the right ingredients.

Eat more,

I was the same and it took me eating 4000 calories a day to get to 12st, I was doing a fair amount of weight training as well, it was hard work though as that was 4000calories of clean food not just eating junk

I’ve now slid back down to 11st as I stopped training and don’t eat as much as I should

I went from 150 at 6'5" to 192 and now am down to 170. Biggest thing is steps, first count calories to figure out what you need to eat to gain weight. you need 3500 calories extra to gain 1lb. After you get that down go to the gym 3 times a week is good, I always suggest to hire a trainer to help you out at first. Then once you have that down you will develop body dysmorphia and start watching protein how defined you are how you could always be better. JK on the last part, some truth to it though. The Biggest thing to do is stay consistent it takes years to get good enough at all this to make huge changes.

I was 135 at 6'1 when I was 18. Hit the gym 6x/week and ate I think 2700 calories /day trying to hit 1g of protein / 1lb of bodyweight. I think I went from 135 --> 160-165 in a year and hung around there for a while, then bulked to 200 the summer after eating ~3500 calories / day, gymming 6x/week. Note that this weight gain is DEFINITELY not just from muscle XD

Lol, the opposite of fat shaming. Skinny shaming. Maybe he's naturally like that.

High calorie dense, healthy foods with a focus on protein and weight training done with slow, controlled reps that are progressively getting heavier

If he smokes cigarettes that can suppress his appetite.

You gotta eat. I read a story years ago about a skinny pro bodybuilder who would wake up at night to eat an extra meal so he could gain weight. It worked

Bro's just like me but during covid all I did was order takeout and not leave the house so I peaked at 150lbs (I'm also 6'0ft). Now I'm back to my regular activities and much skinnier 😭

DRINKING YOUR CALORIES!!! I could never gain weight. Tried eating more but sitting there trying to eat multiple chicken breasts or whatever is exhausting. I found success by eating a big breakfast then adding one or two smoothies to my normal daily routine. I did peanut butter, banana and milk with ice in the blender. You can add a scoop of protein. Mine were about 700 calories.

People sympathise with overweight people on their struggle to reduce their weight. That sympathy isn't extended to underweight people trying to go the other way and it is just as difficult. No advice per se OP but best of luck. Having someone support you in a tough challenge makes it a little easier.

Eating once a day pretty much corresponds with his weight and is the first thing that really isn't healthy.

Doesn't have to be fat-heavy foods, but make it at least 3 meals a day with some light snacks inbetween to raise his caloric intake and watch how things go.

i'm very tall and skinny and if i intentionally try to gain weight it just gives me man-boobs and love-handles...

it's called being an ectomorph and it's not necessarily unhealthy

Some people are just predestined to be skinny. I’m that guy. I weighed 130 when I joined the navy. 25 years later I’m only up to around 150. I eat whatever I want, whenever I want and I eat a lot!!! I got kicked out of a Chinese buffet once. I go to the gym. I’ve tried protein shakes and even the weight gain shakes. It was supposed to catch up to me at 30 and 40. Maybe it’ll catch up to me when I’m 50. Maybe.

There is no naturally skinny. Eat well and work out and you will discover this.

There is no "dirty" or "clean", only calories....the human body needs fat to survive.

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Check out mypersonalfitnesspal.com It helped for an accounting.

More small meals than few big meals, protein powder he can mix with something (I like to put caramel-flavored protein powder in ice coffee), enough carbs for energy boosts.

It’s really as simple as eating more.

Log what he’s eating, add up the calories and aim for 3000 initially. If he’s not putting up weight, go up by 500. Measure weekly, track progress. After a while you won’t even need to log because it’ll be clear what foods have what calories. If he is far below target calories for the day some foods that are ok health wise can be high in calories, like almonds and protein cheese.

Just to be clear, while lifting is very good for your general health, he doesn’t need to be putting on all the weight in muscle. As long as he’s being active and the foods he’s eating aren’t processed garbage, don’t fixate on trying to turn him in to something he’s not. He’ll be healthy.

If he ever needs to lose weight, exact same logic in reverse applies. Start at 2000.

I was 140 when I joined the army at 18 and 6'1". Got out at 175 and dropped to 155 as of last year. Now, I'm at 185.

It sounds patronizing, but EAT MORE. If he's anything like me (given his physique it sounds to be the case), he needs to eat until he practically feels sick. Here are a few things:

-Look up 1000 calorie breakfast smoothies

-Make sure to always be carrying snacks around like trailmix, jerky, fruit, etc

-Get on a routine as to not sleep through meal times

-Working out can really help with that feeling of eating to much, and is recommended. (For me it wasn't necessary until I got over 175)

Go to the gym, it'll help him build a bigger appetite so he can eat more. If you want him to get chubby, let him stop going to the gym and the appetite will stay.

Dates, peanut butter, olive oil in everything, whole eggs, honey

I went from 120 to 155 in 5 years. Just forced myself to eat more. (Not junk food.)

If you're gonna do protein to gain weight, make sure you're getting a mass gainer. Some are around 1400 calories. Unfortunately, they're a bit "heavy" and may make him not have much appetite

When I was 30 I weighed about 165-170 pounds (I’m 6’4”). I got to 190 in four months by eating three meals a day, protein shakes with oats in them, lifting heavy (80%+ of max) four times a week and drinking a gallon(!) of whole milk everyday. I also “snacked” on calorie-dense foods like dried bananas, pancakes, random cereal, raisins. I eventually got up to 250, but I didn’t like it, so I backed off to 220. I’m now dadbod comfortable at 230.

Edit: He has to lift weights, eating more will come with increased physical activity.

Wow I'm not a man but this question got my interest. I'm also thin and struggle to eat enough and I've never been in a relationship where my partner would make this big an effort to help me, other than buy me ice cream or tell me to eat more. BTW, neither of those work. He's lucky that you care and are doing all the supportive work! I'm still trying to gain, I think nuts are really helpful, its really about increasing calories. I work out almost everyday too, lifting is great.

Check for hyperthyroid issues.

I’m in a similar boat. I believe most people have a “default weight” that they regress to when they neglect their health. For some people this means gaining weight, for others (the man your talking about and myself included) lose weight.

This is by no means complete, but maintain routine - gym and diet.

Side note, tall skinny guys have a higher chance of a condition called “spontaneous pneumothorax” so if he’s being active or doing something strenuous and suddenly becomes short of breath have him go right to the ER. Seen a few friends/co workers “pop a lung” this way

I only found one thing that worked and it wasn't healthy so I didn't do it long. I was basically stuck until i turned 38, then I finally filled out.

Oh boy do I have some tips for y'all.

So for context, I've always struggled with weight too. My worst was 106 pounds, and I'm 6'1". I've gotten back up to 117 but I'm still working on it.

The biggest thing, he will not gain weight if he doesn't eat. Doesn't matter if it's not "the healthiest" option or whatever. If he'll eat a burger then make a burger. Heck throw on some bacon and cheese too.

Also, have him start working out. Doesn't have to be a lot, just whatever he's willing to do. If it starts as 20 push ups a day then that's great, it's progress. But with time try to get him to work out for 30 mins a day. Then eventually an hour a day.

Idk how he is, but for me personally I can't gain weight on food alone. I could eat 8 meals a day and not gain a single freaking pound somehow. But when I add workouts on top of eating, I gain weight and a lot of good weight at that. Doesn't even matter what I eat, as long as I'm eating something and working out I'll gain good weight.

With all that being said, still try to get him to have a balanced diet. Weight won't matter much if he's eating a ton of junk food and never eats veggies or fruits. His body will give out eventually if he has a crap diet.

Edit: I wanted to add, that protein powder and protein shakes will help as well. Powder doesn't seem to work as well, but the protein shakes have helped me tremendously!!

Eat eggs and drink lots of chocolate milk

Been in the same boat, ~5'10" and ~130lbs, tried protein shakes and tried calorie loading but I just can't manage to eat enough and was just making me sick to eat that much. Was an overnight stocker for 4 years and was constantly moving and getting exercise. I think genetics plays into it a bit, the only time I ever really put on weight was drinking beer in college and it only added about 5 to 10 lbs. I've just gone back to only really eating once a day with home made pizza and pasta. I did eat a lot of protein while I was working but if you find anything that works let me know! I've been hoping to find a woman that'll fatten me up lol.

Besides just shoving more calories down the throat he really needs to work out. That'll make sure that the weight goes on as muscles and not flab around the waist. Probably the best way to get him to work out would be to work out with him.

Eat more, particularly calorie dense foods. Don’t skip meals or snacks!

Basically, eating 500 calories more per day than he is currently eating will add on about 1lb per week. For me what works is to eat a healthy diet and then add the 500 in whatever way I want. Beer, ice cream, fries, whatever. That way I actually do it. I am 6’ and struggle to stay at 160.

Drink as much Whole Milk as you can in addition to your regular food. Drinking calories is easier than eating them

I am about to say a Really a far fetched scenario and a lot of factors might be in play here but there is a possibility of some form of cancer. I am a cancer survivor and one of the things that doctors always told me was that you start losing weight fast as a symtom. Other symptoms being sweating at night, don't feel like eating etc.

I missed the "healthy" part when I initially came to reply. I was simply going to say a steady diet of fast food and soda will do the trick.

Lift heavy. Eat properly. Sleep well. It works.

Oh, and patience.

I’ve been skinny pretty much my whole life. Over the past few years I’ve gone from like 155 to 185. Just eat a ton. Definitely still try to eat healthy but don’t think twice about pizza, burgers, or anything like that. Then, at the end of the day, drink a protein shake with mass gainer.

Could be low testosterone. But also need to eat & workout will help gain weight. I’m 6’2” and went from 165lbs skin and bone to 235lbs muscle in just two years. Can’t skip meal or a workout. Mass gainer shakes help. Stick to whole food

What has helped me as a lifelong scrawny guy is changing the way I eat. I used to eat just 1-2 big meals a day, and no matter how much i worked out I couldn't gain mass. But changing to eating roughly the same amount spread over about 4-6 meals a day helped me gain 25 pounds in the last 3 months or so with no other major changes made to my lifestyle.

First, I would consult his Dr. And/or a nutritionist. Everybody is different when it comes to weight gain/ loss. On that same note, what might be unhealthy for one person is just fine for another.

I personally (due to a medical condition) struggle to gain and maintain weight. What works for me (but maybe not everyone) is to eat all the fattening foods I want/can. Protein shakes can work, but mostly those help with muscle growth and never really did much for me. (Maybe now that I'm going to the gym, they might help.)

Let him eat all the burgers, Chili chesse fries, pancakes, potatoes, etc. he wants. Also, make sure he is eating until he feels full.

lots of protein and lift weights A good book that I learned lot from is called bigger leaner stronger

I am currently and have been for the last six years a professional bodybuilder with three natural world titles and two natural universe titles. Do you have to solve what I called the volume dilemma… You can work out all day and do anything you want in terms of supplements but if your diet isn’t there, then you’re not going to gain weight or size. Solving the volume dilemma works like this… Most people will tell you just to eat a bunch of food, but realistically short guys and small guys like myself… I was 5 foot 5 and only 117 pounds when I joined the military and started Bodybuilding… We can’t just jam more food in and expect not to puke or even worse rupture our stomachs. You need to find calorically dense foods that will give you a much higher caloric intake without filling your belly so much. For example, most people can take down a wrap much faster than they can handle a full-size bagel. They have the same amount of fat and carbohydrates if you know how to pick them. Same thing with your fat contact… A couple tablespoons of peanut butter usually goes down much easier and by itself rather than let’s say cheese or fat yogurt. Anyway, I hope this helps!

Like one of the people said here, try to let him eat a SURPLUS every single day. what also helps is to drink weightgainer or Whey before he goes to sleep. It will slowly work in his stomach and pick up protein from it.

I’ll keep it simple: eat a lot of protein, go to the gym consistently, and a large of carbs like pasta. A dirty bulk of 3000-3500 calories could work to. Like pizza, burgers, and fried foods would help. it helped my little brother gain weight to be at a comfortable weight. He went from 110 to 165 in about a year and a half while going to the gym and he’s also 5’11 so same boat.

I just want to add: I am down about there from about 160 due to celiac disease. It triggered a couple years ago and I rapidly lost weight and can’t get it back on. Could be a health thing that he needs to have checked out. Good luck and you sound like a great partner to him

His issue sounds like not being able to eat much ( one meal a day thing). A member of my family 6’ and 140lbs struggles to eat. When he ate one big meal a day he was about 110 lbs. By forcing himself to eat more ( 2X daily protein shake with dairy cream & oat flour) and by weightlifting daily he gained 30+ lbs in 18 months. He has to count macros closely to gain. His major struggle is eating enough calories per day , he has to set timers to force himself to eat. The irony, people think he is so fortunate being skinny. He hates it.

I've always struggled with being skinny until this spring when I finally managed to gain 15 pounds. My trick was adding multiple different courses to my meals. I realized there's a difference between being full and being tired of the thing I was eating. There is no way I could ever possibly eat two chipotle burritos in a row. That's friggin' gross. However, it turns out I can eat a chipotle burrito and then have a smoothie and then have a piece of fruit and I never feel like I'm force feeding myself, I enjoy all of it.

I think just getting him on a regular 3 meals a day routine is a good start. Eating once a day is probably what's keeping him at that low weight.

Try to keep yourself happy. Happy cow spread happy. Happy cow eats happy.

He should try working out. Not running, but lifting weights, pushups, rowing, exercises that build muscle. Muscle stays on your frame a lot longer than fat does, and working out also increases your appetite.

Get him some South Asian sweets and delicacies once a month.

Besides that, exercise (even isometric ones help) and eat protein.

I would eat and eat then top everything off with a quart of WHOLE chocolate milk. I went from 135 to 180 on a 6’1 frame in a matter of a few months. I lowered my cardio and upped my weight training. Now, I’m opposite 6’1 220 and I Lift heavier and do more cardio. Once I hit 30 weight gain became easy.

I think the easiest way is to just drink one mass shake before going to bed. The most important ingredients are milk, oat, peanut butter, protein powder, olive oil and a banana. Put it in the blender and you have easy 700-1000 cal. That’s like 1/3 of his daily calorie income. I use strawberry protein powder and frozen strawberry’s for a better taste.

Peanut butter works wonders

im not sure if it was natural or be cause of my anorexia. but i conquered that thru lifting weights and eating better

Get him going to the gym. Go with him.

Im 190cm tall used to be really skinny(eating disorder). Now im above average on weight. Been doing one gainer a day for 3 years. Gained some bellyfat. But overall its something better than nothing. So yeah gainer shakes are good. Would be doing smoothies too but dont own a mixer but its tasty and goes down real easy. Try some yoghurt as as late night meals.

Edit: spelling

Was very skinny all the way up to about 2 years ago.

Get a routine, a breakfast seems to make me want to eat more. Shakes are super useful for anyone who can't eat much.

You gotta lift. Go to the gym. Drink lots of water.

Seems stupid but having a lot of sex helped. Basically anything that got the body moving and then enforcing the idea of eating to recover.

I am still around 155 lbs and don’t struggle to put on weight but I sure as hell can lose it. Best thing you can do to put on weight is to eat way more and weight-lift without too much cardio. I mainly lose weight by not eating or exercising for a few days. This usually looks like me sitting on the couch eating one meal and drinking 125 ml of water. I eat extremely clean, only rice, chicken, banana, orange, broccoli. Runs me about 1000 or so calories, well below my maintenance. In order to gain weight I eat about 3 of these meals a day and will add in waffles just to mix things up. Before my first meal, I usually will exercise using weights. Weightlifting won’t burn that many calories but it will burn fat and replace it with muscle which is heavier than fat. Thus over a period of 2-4 months, I’ll bulk up to 175. The key to this is to literally stuff your mouth and weightlifting each day.

What helped me a lot was instead of eating one big plate for dinner, i'd eat a smaller plate, wait half an hour, and then take another.

I found out i was bad at eating a lot at once, so splitting dinner up into 2 or 3 parts helped me SO much

I've always been a tall slim Guy, bony etc and it used to really bother me. I always found it really hard to gain weight and it bummed me out. I'd eat and eat and eat but I'd just seem to get denser, maybe fill out an inch. In the end I decided to lean into it. Now I'm appreciative of my build, I look like a skeleton wrapped in steel cables and I'm alright with that. I'm healthy and strong sooo fuck it.

Protein and nuts like almonds as snacks. Just get him into calorie surplus

Protein shakes and lifting.

I used to be skinny af, started going to the gym and eating a lot more (drinking a 1000 caloric smoothie helps a lot). I gained muscles and fat but even the fat was worth it. I'm not cutting a bit to lose the fat.

I’ve seen some “mass gainers” floating around Amazon & stuff when I search for my whey protein. Might be something worth checking out as the hardest part about bulking is actually eating enough protein.

I had in the past been really skinny (think machinist- I had a weight problem). I put it on by gym and eating fish (personal taste as I don’t really like chicken or red meat. Nothing political, I just don’t like the taste). That plus veggies and high fat fruits etc like avocado. Just appropriate. Don’t skip meals, snack once between meals with nuts etc

Get married and get your wife pregnant. Took me from 120 to 150 over 2 years.

Going to the gym will give him healthy weight. Muscle is lost slower than fat.

Give this woman a medal

Finally a question for me. To do this right you should use a diet/calorie tracking app. I recommend macrofactor. Have him put in his goal weight (180lb is a decent target) and have him log his calories and weight. It’s literally that easy.

The key thing is he just needs to eat more. It’s easiest to add in an extra meal instead of eating more at each meal. Get him doing some weight lifting and the weight gain will be even better. He will most likely gain some muscle even without the lifting but it will help immensely with his physique.

I used to be tall and skinny, too. Now that I'm in my seventies, I'm trying to get back to that state.

Some point in my late 30s I developed a pot belly. It's like there was a hormone change, and my weight went up my 30 lb or so. After that, I've had to watch what I eat.

Although I was very skinny when I was younger, I never felt weak or lacking in energy. And I would not worry about it, and even take it as a blessing, if there are no other problems caused by a lack of body mass. I mean, enjoy your food! Think of all the people that have to deny their appetites, because they gain weight so easily.

If you want to be in good physical condition, exercise. If you want to bulk up, lift weights. But if you're strong enough and have enough energy, don't worry about it. It's a blessing!

I struggle with this I just don't have much appetite. I find the only way to gain weight is to go to the gym, the exercise naturally boosts my appetite

I’ve always been naturally skinny and had a really hard time gaining weight for college sports. The one thing that helped me tremendously was eating a lot of carbs before bed. I would eat 2-3 bowls of mini wheats every night 30ish minutes before sleep and gained 20 pounds in a 6 month period. Was it all good weight? No. But gaining a lot of weight with a high metabolism is more difficult if you try to eat completely clean.

Exercise, especially resistance training increases the appetite. Food: Meat, eggs, fowl(with skin), full-fat dairy, white rice, and vegetables. Cooking oils: Ghee, butter, avocado oils, coconut oils. An occasional cheat meal would be great too. I am not a fan of protein shakes since they can cause a lot of indigestion, and nasty protein farts as a result which is the last thing that you want. Use some kind of a progression metric in the gym coupled with a gradual increase in calories. Remain consistent and be patient.

Add gainer shakes once a day (protein, peanut butter, banana , oats, milk)

Make sure to shoot for 2-3 legitimate square meals a day

And the real truth: you have to force it sometimes. I didn’t really start gaining weight until I started eating uncomfortable amounts. Eventually your metabolism and appetite will catch up and it won’t be a struggle anymore

I'd actually point at hard-core physical activities as a possible solution. I have to work HARD to hit my goal weight of 180 and my body just sheds weight down to 150 when I slack. I have no appetite except after working out, so I work out until I'm hungry and then pack in as much as I can.

I used to eat 3 buffets/week or more, when I thought my stomach was a “black hole”.

As I grew up, I noticed that I stopped moving. 3000h in overwatch and 20kg up. At least I made top 500 right?

Ended with me not playing that game anymore and then counting my calories. Currently down 12kg. Current weight is 150 lbs, feels alright for my height at 5’8. Although having a six pack is my current dream.

Can’t eat? Consume shakes. Don’t like gainers with artificial sugar? Add bananas and peanut butter. Now you have natural sugars. Should be marginally more healthy.

What did I train during my “black hole” days? Mma. Picked it back up after my weight gain. Was a great help. That and walking more.

I mean, what's the question here? He doesn't eat enough food to weigh what would be normal.

It's not like he's eating a normal diet and unable to keep weight on. He's barely eating and doesn't weigh much - this is pretty obvious cause and effect.

I also don't really see why it's your responsibility to fix his problem. Being a functional adult that typically eats more than once a day isn't that hard, and if he's got an eating disorder/psychological problem he should go seek out help for that.

With that said, he's only slightly into underweight territory, if his doctor has no problems with his numbers, he's fine with his life and not lethargic or grumpy all the time, and he doesn't have an eating disorder, there's not necessarily an inherent problem here.

I got married at age 23. I was 6 feet 135. Very similar. A few years later I applied to several government agencies where I didn’t meet the physical weight requirements, just too skinny. I went on a bit weight gaining crusade to get up to the minimums. Would eat a dozen eggs every night before bed, weight/protein shakes. Nothing worked.
Fast forward to now. I’m 50 years old. 6 feet 180lbs, feel great, very active, in shape.
For some people their metabolism just needs time to level off