When does being underweight become dangerous for runners?

I'm in a similar situation

. anywhere we can PM bro?

BMI is mostly inaccurate for athletes as muscle weighs more than fat. You can have one individual that is 5'8 110 and has lean muscle VS an individual with little to no muscle tone and never exercises that is also the same weight due to simply undereating but their health could be dramatically different.

There are also people who are just more likely to be thin due to their genetics or body type (ectomorph). When a person who is naturally underweight with a healthy diet and moderate exercise picks up competitive running, running all those miles even with a good diet could result in them being even thinner but not drastically as unhealthy compared to other individuals.

For example, say you have someone who would normally be 5'8 and 160 pounds with a healthy diet and moderate exercise and has a mesomorph body type. This person could lose weight by undereating and exercising excessively and eventually get to 5'8 and 110. This person isn't normally at this weight, so to try to sustain this weight, they could put their body at risk for injuries and other complications.

For someone who is 5'8 and 160 with a sedentary lifestyle and then with a restrictive diet loses weight to get to 110 pounds... it would also be unhealthy for them if they would normally not weigh this much compared to if they were active and healthy.

You could also have someone who has always been underweight their entire life despite eating a healthy diet and exercising moderately. They could be 5'8 and 110 just like you and would normally be 115 when they aren't running high mileage for example. This person most likely not be as unhealthy and not be as injury prone as other individuals with the same BMI with the above examples because their size is mostly natural/genetic for them and not the result of excessive exercise or a calorie restrictive diet.

Everyone's body is different, if you feel pain or discomfort at the weight that you are, then you should gain weight. If you are feeling drained after workouts or feel like you aren't eating enough to feel FUELED and ENERGIZED then gaining weight could be good for you. If not, don't force yourself to gain weight that would be more of a stress or pain compared to gaining health and energy. Height, weight, bmi etc. are just numbers, focus on health and what makes your body feel healthy and strong when you run.

yeah what works best for you?

ListenToYourBodyNot#s wrote:

BMI is mostly inaccurate for athletes as muscle weighs more than fat.

No.

Honestly mate, I think there’s a large chance you may have an eating disorder. :( As a middle distance runner, your bmi being under 18 is where it starts to get detrimental because that’s when your strength to weight ratio starts to get compromised, drop into the 15 or 16 bmi range and that’s where it starts to get compromised a LOT. You probably have the cardiovascular strength to run at sub 5 paces but at your bmi will not have the musculature to propel your body forward at the speeds you want.

Most middle distance runners have bmis of around 20-22 before they try and get in shape which means their strength to weight will be optimal but their cardiovascular conditioning won’t be, this is where the 2 secs per lb rule comes in but as stated before - it only really works for people where weight and conditioning is their main limiter. It is not your main limiter, strength is. You should gain.

Your very low weight is also why you will find it hard to adapt to training and reach a plateau because you can’t improve (at least not without getting injured or overtrained) because your body cannot adapt to run faster paces unless it is relaxed. Strength is important to hold form.

I get that you may also be light because you don’t want to put crap into your body but there are lots of high calorie clean foods you can eat to gain weight. Pasta, nut butters, if you are into baking you should look up some paleo chocolate cookie recipes!

And also, I hope you are sharing what you are telling us with your doctor, coach and any therapists you may see.

I'm 16, 5ft 9 and 96lbs. I'm struggling to gain weight.

jojorunner wrote:

15 pounds? Won’t that make me significantly slower?

No, you are too skinny to be strong. You need to be strong to be fast. Put on some muscle and watch your times drop. Your slow 800 times point to this - you need to be strong to run a good 800 and you are weak.

I weigh 50 pounds more than you, am probably 20 years older, and can run your PRs today. An extra 10-15 lbs of muscle will only help you be stronger. Don't worry about it at all. You need it to improve.

Its always good to eat healthy, but you need to eat probably twice what you already are to put on some weight. Try adding some ensure or meal replacement drinks if you don't think you can eat more. Bottom line is, you need more energy.

Runner86 wrote:

I'm 16, 5ft 9 and 96lbs. I'm struggling to gain weight.

That is really quite a dangerously low weight. Why are you struggling to gain weight? Add in lots of little snacks, avocado and eggs, what about brownies, muffins, milkshakes - there's lots of things you can try. Have a look at recipes on youtube and pictures of food - go for whatever takes your fancy! At that weight there's probably not much you can eat that's bad. You need an extra 3500 kcal to gain 1lb. So that's an extra 500 kcal a day to gain 1lb per week which seems reasonable. Obviously there is variation each week due to water weight and so on, so I wouldn't weigh yourself every week - that's the weight gain you'd be going for ON AVERAGE over the course of a month. Make your own pizza, you could have veggie/salad items with dips, chips and nuts, nice pieces of meat. If you think it'd be easier to drink the calories there are loads of good milkshake recipes online as well. You can even get milkshakes that are 2000 kcal per shake...

Sounds like you are a gangly teenager going through a growth spurt.

I think you are more prone to getting sick - colds, flu things like that - when your bodyfat drops below a certain level