Many of us know the health risks associated with being overweight or obese – but we’re not always aware of how dangerous it can be to be underweight.
Being too thin is worse for your health than being slightly overweight, and there are a number of complications associated with having a BMI of under 18.5 (the official definition of “underweight”).
For many people being underweight means their bones aren’t as strong as they could be and they have fewer ‘reserves’ if they fall ill. It can also affect a woman’s fertility.
- BBC health
Here are seven health problems which can be caused by being underweight:
1. Weak immune system
If you’re underweight, you’re probably not taking in enough nutrients. This affects your body’s immune system, making it more likely that you’ll catch a cold, flu, or whatever else is going around.
2. Low muscle mass
Particularly when being underweight is caused by illness or deliberate food restriction, people who are thin are likely to have a low muscle mass. In teenagers in particular, who are still growing, being underweight can mean that muscles don’t develop well.
3. Hair loss
Being underweight affects your hair – often meaning that you lose hair from your head. You may also end up growing body hair in odd places (especially if you’re female) if you’re too thin. Your hair, just like your body, needs to be nourished by adequate food intake.
4. Osteoporosis
Also known as “brittle bones”, osteoporosis makes fractures much more likely. This can be an especial danger if you’re underweight because you do a lot of sport and don’t take in enough energy. Women who have passed the menopause are at especial risk of osteoporosis.
5. Anemia
Anemia occurs when the body cannot transport enough oxygen around in red blood cells. It’s often caused by iron deficiencies – not uncommon in women, especially those who are dieting or restricting food intake. Anaemia can make you feel exhausted and can cause heart palpitations and dizziness or fainting.
6. Menstrual irregularities
If you’re female, your periods can become irregular or stop altogether (known as amenorrhea) when you’re underweight. This is because your body thinks you’re starving – if you’re not taking in enough food to stay at a healthy weight, your body definitely doesn’t want to be giving what little energy you have to a baby.
7. Pregnancy complications (or unable to get pregnant)
Even if your periods don’t stop, you’ll have trouble conceiving if you’re underweight. And it can be extremely dangerous for the growing embryo if the mother is too thin: a study by the London School of Hygiene and Tropical Medicine found that:
Women who are very underweight before they become pregnant are 72% more likely to miscarry in the first three months of pregnancy.
Are You Underweight?
If your BMI is under 18.5 (you can find your BMI here), you’re underweight. Even if your BMI is between 18.5 and 20, you are thin for your height and could suffer from some of the problems above.
Your doctor will be able to help if you are experiencing symptoms that you think might be caused by being underweight – please get the advice of a medical professional if you’re at all concerned.
Over weight is better than under weight. My oldest child who is anerexic, autistic, high motabolizim.
Now needs a feeding tube and is diagnosed Failure to thrive!! It’s worse when you’re prone for infections and as a parent you can’t help your child in needs to help!! He also has a Dificancy. You get prone to these sicknesses!!
My child is that way. He is anerexic with feeding problems and high matabolizm.
He’s going to need a feeding tube because of it. Having extra weight is really better Heath
Wise. You don’t need a feeding tube to survive and diagnosed Failure to Thrive!!
Yes well you lost the weight in an un- healthy manner so your body was probably not reacting well to that. Being underweight naturally is different. I am somebody who has been naturally very thin my whole life, and I eat more than most of the people I know. My doctors have always told me I am very healthy it is just the way I am built. I guess what I am trying to say is a healthy body is one that is naturally what you are supposed to have.
I’m 28 and my BMI is below 18.5 just slightly. It’s something like 18.2. I have always been underweight, my whole life. I have a small frame & don’t look bony or boyish at all. People have even described me as “shapely”.
I eat plenty and mostly healthy food but with some indulgences. I do yoga once a week & walk a lot. I make no effort to sustain or change my weight; it is what it is.
I have NONE of those health issues or any health issue at all. I’m very healthy. I rarely get sick, my periods are regular, I have thick glossy hair, etc. I truly think this only applies to people who are severely underweight, not a few lbs underweight.
I have seen studies which show that being a few lbs underweight as a woman is a non-issue – there are no increased health risks. Being underweight poses a problem when it’s severe and/or for the elderly.
I’m tired of the scare tactics average fat people use to make naturally thin people feel bad. I really think it stems from bitterness, not any true concern.
I’m a 19 year old male, I’m 5’8 136 lbs, which puts me at a BMI of 20.5. Which, according to my doctor, is completely ideal for just about anyone. The thing is, I still look thin and I’ve just started working out, and I’ll gain weight once I put on more muscle. That’s why I think that BMI can be very flawed. Lets say over the course of the next two years, I work my way up to 165 lbs (hypothetically ofcourse, I doubt I’ll gain THAT much), that would put me at borderline overweight, which seems ridiculous. Because I would look more muscular and probably healthier. I’ve heard that the majority of male athletes are at least borderline to slightly overweight according to their BMI. That is why I agree with the above poster who said that the body fat test would be a more accurate measure of body health.
Question…I went to my gyno the other day. I weighed 106, 1 pound less than what I weighed when I was there last month. In November I weighed 126. The weight loss is due to stress. I am having some health issues because of the drastic weight loss but if I’m not hungry I can’t eat. I do eat sometimes. Before I left he told me he wants me to come back in on 4-1 to weigh and if I weigh around 100 pounds he might consider putting me in the hospital. Can he do that? What would be the point in that? What would they do for me in the hospital?
Better to have a bit lower weight than to have higher than required. Being fat is not an acceptable thing for anyone, but really the BMI is the right indicator. If one is thin but the right BMI, its a great thing. I personally feel thin (underweight or not) is better than big fat (overweight).
What Kristen said is true, also it’s not uncommon for children/teens who are still growing (or have just recently finished growing) to have a BMI that is slightly lower or higher than what is recommended for their age & height. So long as you aren’t experiencing any health problems because of it & your physician says you’re overall healthy don’t worry about it too much =)
I think the BMI is not quite a one-fits all solution even for the lower end of it. Even though the BMI may be less flawed in determining if you’re underweight, it still does not account for your frame, i.e. if you’re small-boned or big-boned. Did you know that Singapore/Japan consider a BMI of 23 to be overweight? That’s because all the girls there are tiny to start with. Being Asian, I have the same frame as those girls, which means I’m 5’2″ 103 lbs, and healthy. I eat good portions and I do have both fat and muscles on my body. I don’t have any of the problems described above but I take calcium supplements to avoid osteoporosis in later life. Also, as mentioned by other people, fast metabolism is another culprit in keeping low weight. So while there are health risks associated with being underweight and it is good to be aware of them (thanks for posting this article), I wouldn’t start freaking out about having a low BMI unless you are actually being malnourished or have some eating disorder. Everyone is built differently. I feel the article should be a little more careful in making broad statements using just based on BMI =) Starving yourself to fit in a size 0 is definitely unhealthy. Eating healthy, exercising (not overly!) and fitting in a size 0 is not as big of a deal.
I’m considered underweight and have none of those problems, especially not anemia because I have a rather balanced nutrition and take lots of dairy products. I’m female, 28 years of age, 5’3, weight 95 lb. My hair is abundant, my hemoglobin levels are always above 14.5, my white blood cell count is always normal.
I have a lot of trouble gaining weight, and have been diagnosed with PCOS. I believe BMI is too deceiving, people should really stop trying to find cookie cutter solutions for their health issues, especially when they are related to weight. People with weight issues should consult with their doctor instead of just calculating their BMI and trying to convince themselves that they are fine. I think it’s dangerous to ask “which is worse”, because each particular case is different, people get comfortable with their weight when they read this kind of things, although they don’t know the causes or consequences of their weight issues, be it under or overweight.
I have an unusual food intolerance (vinegar), which in college caused me to lose 20 lbs. I’m 5’6″ and weighed 118 lbs in the beginning of college. At my lowest, I was 97 lbs. I would try to stay away from problem foods, but the slightest bit of vinegar would make me sick. I was constantly tired (I slept on average 12 hours a day at the lowest weight) and almost always sick. I was put on a junk food diet in order to just simply gain weight or I was going to be hospitalized.
Three years out of college, I am back to a normal weight and feel so much better. Controlling what goes in my own food makes all the difference, so eating out is the biggest risk. Sadly, everyone either thought I had an eating disorder in college or didn’t even notice there was any problem.
To Kristen: very well explained! It indeed doesn’t mean that this will happen to everyone. I’m just 5’3 and now weigh about 115 pounds. When I was 17 my body weight dropped till 90 pounds and my BMI was about 16. I was sick practically all the time during at least a year. I was cold all the time, very pale, my hair fell out in chunks, I was totally exhausted, my mood was quite bipolar. I was obsessed with food, counted calories, cleaned all the time, could only accept straight A’s, didn’t want to see anyone or talk to anyone. I lost my periods, hair started to grow on my back, I had lots of headaches and colds, my nails broke and my skin looked awful. I have a rather large skeleton and was always the shortest at home or in the class room. No matter how hard I tried, I could never look like the other pretty, perfect and happy girls. Now I’m 21 and still think I’m huge. You know that you’re not really fat, but some part of you still keeps telling you that. I messed up my metabolism and hormone levels. It will be hard to ever have a baby or to accept yourself as a real woman. We’re all intelligent young people with plans and ideals, but we’re so vulnerable. It’s very important to love yourself and to accept that you can never be a Hollywood star or Einstein, but that you still are beautiful, good and worthy of respect. Thank you for starting this blog!
PS: I am fifty years old.
Strange that I have never suffered any of these illnesses or disorders, though my BMI has always been around 17.5 (male, 5’10″, 123#) (actually 123# is an increase of about five pounds in the last couple months).
It apparently wasn’t a problem with the Navy either, where I served a full enlisted career.
Underweight people sometimes have high metabolisms. I eat ALOT and have a healthy diet yet I am a little underweight. It’s because I have a very high metabolism….I only gain like 2 pounds each year. I hate when people say to me, “You need to eat more you’re so skinny” when it isn’t because I don’t eat alot. I eat like a pig compared to my friends.
Hi, I am 18 and am 5′ 5.5″. I have been told that I should weigh at LEAST 115 pounds, however, my weight never gets any higher than 108. Actually, in the passed week, I have dropped to 105 lbs. I have been struggling with trying to gain weight for about two years. Three years ago, I was at a healthy weight, but was depressed and began starving myself, and lost a significant amount of weight. I began working out and eating right after a while and gained a little weight, but lost it all again. I can’t seem to get my weight to where it needs to be. My periods are now on a six month schedule and they are VERY painful and VERY heavy. I don’t know if it is just my being underweight or if it is because of other health issues because of my weight. I don’t know what to do. I am going back to the doctor in two months and am hoping they will help me this time. Until then, can someone give me some information?
hi im natuarly skinny and always have been im now 17 yrs old and im 5ft 9 inch and weight around 8 stone 8 lbs and i havent felt any of your symtoms you say i could get and over the last year i realy havent done much excersise at all and i eat a lot of sugary sweet of course i know i need to to cut back on sweets and get my regular excersie but waht i want to know is whats the easyest wya to starta regular routine when you could say ive lost my self physical as about a year ago i was doing my regular excersie and eating to much food now ive lost my regular food patern and find it hard to get of my arss to get excersie im probaly lazy but do you have a solution
i also rabbit on to much
Everyone’s body is differnt. Some people will have health issues, such as loss of period as mentioned above, at a BMI of 19, and some not unless their BMI is below 17. No one is saying that if you are underweight you will die the second you become so. What is being said is that for the average body, there is a range of a healthy weight to height ratio. Your health risks increase if the ratio is below the “normal range.” This does not mean that you will lose your hair below it, or stop your period, or have a lower immune system. It means that the chances of those and other health issues increase, and the farther away from the normal range that you go, the more those risks increase.
Your BMI is 20.3, which is in the normal range.
The BMI ranges you see here are for “Adults” defined as 20 years or older. Online you can view charts for children’s BMIs; anything under the 5th percentile, is underweight. For a 17 year old, a BMI under 17.5 is underweight. To be in the normal/healthy range, you need to be at least 108.5 lbs. Next year (18 yrs old), the healthy BMI begins just over 18, or 112 lbs (provided you are done growing taller).
This is interesting. I think every case is different. In the last 6 months I have had:
3 instances of bronchitis- each lasting about 2-3 weeks
Strep throat
a Urinary Tract Infection
The flu
Weird symptoms- excessive heat/fever, insomnia, excessive hunger, (in february) was eating 3 X my normal intake for about a month and a half and my weight was going down, within an hour of a huge meal my stomach would start grumbling again
I was much heavier when I was on a mood stabiliser for about 2 years, I gained up to a BMI of 24 at my highest and lost w diet and exercise down to 22 before I stopped the medicine. Had never been that heavy in my life.
Anyway went off the medicine mid-late last yr, and went through an incredible stressful/traumatic emotional phase over new year and christmas and lost down to a BMI of about 19. Had a broken heart and a series of traumas where I would lose small increments of weight but not gain it back despite resuming normal eating patterns.
Currently I have no idea where I am because I avoid weighing myself but I don’t look well. I’m not as thin as some, probably could be anything between 18.5 and 18.7, but my body has reacted badly to the stressors. I love food and i eat what I want, but I have a very busy work schedule and often work comes first and I probably don’t get the nutrients I need even though I have a good appetite.
I don’t eat regular meals, I snack alot through out the day (on the run usually) and I’m not really a breakfast person, I might have my first ‘meal’ anywhere between 11:00am and 3:00pm depending on my schedule/commitments for the day, but then I am snacking throughout the rest of the day and my portions are probably more on the small side but I eat regularly.
Anyway have just come down w a really bad case of the flu that drains me so badly to the point where I am just passing out randomly, I get winded walking up the stairs, I struggle to find the energy to do simple tasks like have a shower and prepare meals etc. and I’m wondering if it’s normal that I’ve been sick so many times and my symptoms are so severe now, because it’s not like I have a BMI of 14 or something and I’m really physically frail and weak.
When I had a BMI of 20-24 I used to be able to go to the gym alot (maybe 5-6 days a week) for an hour but now I can’t last 2 X 20 minutes a week, and I get exhausted doing the most menial things.
I don’t know if this is even weight-related or I’m just imagining it, I might just be a hypochondriac?
not every fashion model stave themselves and some people are just naturally thin… and its hard to gain weight….. an d i also model because i love doing it and i dont have any of theses problems im healthy and i pefer to be slim thats just me i dont understand why we cant all just accept that not everyone is suppose to look the same this world is full of ppl that hate
My BMI is 16.6 and i’m 5’6ft and 17 years and 103 pounds.
Yet I have not been told i’m underweight by my gp even though i went to see him a few weeks ago because i contracted an infection. So I am possibly a healthy weight?
I am 13 and my BMI is 16.7. I am 5’11” (I like to say I’m 6’0”) and weigh 120 lbs. I don’t really experience any of the problems above that I can have except that I have barely any muscles. I barely ever get sick, I’ve never broken a bone and I grow hair (on my head) pretty quick. It’s kind of weird.
im 5’5” and i weigh in at 117 at the moment with bmi of 19.3. im an athlete and very muscular, but if i go below 19 bmi my period stops and i get sick. so every ones different =P i think its based on your body build. bone mass, muscle mass, and fat
Thank you for reminding me that WE NEED FOOD! The world tells me – all of us! – otherwise!
This is inaccurate. Being slightly overweight carries the same risks as being slightly underweight. Being overweight is probably more dangerous because of heart disease and diabetes which affect more people in this country than mineral or vitamin deficiencies.
I agree with Vicky. My BMI is 17.5. I’m 5’5″ and weigh 105 lbs. I consume a high calorie diet and have been unable to gain weight all my life. I do not exhibit the hair loss or weak immune system because I never get sick as often as my family or friends and I’m exposed to sickness on a daily basis because I have worked in a hospital for many yrs. I’m 24 yrs old and I cannot stand how I am thin automatically means I have an eating disorder in most people’s eyes. I believe it is just as hard to gain weight as it is to lose a couple of lbs.
i agree with vicky – some ppl have naturally high metabolisms etc.
but whatever it is – we are all different: ie. diff body types/shapes too.
its true that underweight ppl who are having EATING DISORDERS or severely dieting/restricting nutrients will fall into the categories of symptoms you listed.
the body is amazing – it will have a specific set point where all func are normal and working well. throw that off balance and you’ll pay for it. wont happen STRAIGHT away, but it will.
From personal experience – I have many health conditions incl poor circulation, autoimmune disease and digestive diseases. i was at my worst about 2 years ago, and was very malnourished due to stomach, liver and pancreatic problems. i was very, very underweight and sick (not eating disorder). of course people thought i had eating disorders or cancer and such things. Anyway – i experienced almost ALL of the symptoms, most noticably amenorrhea, loss of muscle mass, iron and many many other nutrient deficiencies, MASSIVE HAIR LOSS (< – is absolutely, i warn you, NO FUN if your female [or male!!]) and heart problems.. probably due to malnutrition wasting my muscles.
Its been very slow but i have recently improved with my recovery. I feel much, much healthier than when I fell sick. I still have health problems going on, but those are permanent and cannot be treated. AS FAR AS weight is concerned – im at my healthy weight, though I’m naturally on the thin side (BMI 18.5). So imagine when I was sick and lost even MORE weight – my body was in HAVOC.
To all people who are fixated with dieting or thinking about going on severe/low calorie diets : please, please think again. you gotta have a balanced diet, exercise and lifestlye. you cant sit and chew carrots all day or only eat 400 calories… you’ll end up intentionally starving your body. All your healthy organs…. unlike me – i had NO CHOICE since i had digestive issues in first place that interferred hell alot with my nutrient intakes. you dont want to end up getting too underweight, or even an eating disorder, and ruin your already perfectly healthy body. you dont want to stay in hospital with a FEEDING tube. that happens to ppl who are sick (not eating disorders) too if they have malabsorptions. they DONT have a choice. but you can make more sensible choices and its following a healthy, balanced diet.
sorry about the rant guys… i just had to say all of this. i had to go through being sick and severely malnourished and all the symptoms almost, literally KILLED me. physically and mentally. its no fun at all.
I will highlight: to me losing HAIR was one of the WORST parts ever. i lost about 70% of my hair. it just kept falling out in clumps and clumps. my nails wouldnt grow either. wounds wouldnt heal. i was sick every other month….. the list GOES ON.
Even a small restrictive diet has been shown to cause dermatological problems like hair loss (telogen effluvium) . PLEASE LOOK UP TELOGEN EFFLUVIUM and DIETING it will give you so much more information.
So some, and luckily me, my hair grew back, fully again. Some aren’t that lucky – when hair loss has been triggered it might stay or ‘morph’ to genetic hair loss = hair thats lost forever, and unable to regain their initial hair density.
PLEASE PLEASE….. just, consider what you’ll put your body through..what you’ll lose… if you take things to the EXTREME when you STILL HAVE A CHOICE TO NOT TO!!
If your at a healthy weight, don’t even bother ‘losing weight’ – it will throw your body off balance. what comes next wont be fun !
If you have/think you are getting and eating disorder, please see someone for help. i have not had eating disorders but the end result for malnutrition for sick ppl is THE SAME. same symptoms. its not pretty AT ALL.
Thanks for reading guys……. best wishes
Dee