Yes there are physiological problems associated with low body fat, however I believe the limit for men is nominally 3%. (I'm guessing at 6'4 and named Ken you are a man.)

Notice-I am not a medical professional!! So take this for what it is worth....

I would see your doctor, possibly to check for EBV (mono) type lingering infection. This could explain your recurrent colds and your weight loss. So I am guessing that your weight loss, and lower BF, is not causing your colds but has a common cause.

-Richard

I'm no doctor and I certainly don't want to scare you. But, you should go to a doctor asap and get yourself checked out. My mother was once incorrectly diagnosed with lymphoma. Based on the research I had done, symptoms include: flu like symptoms, night sweats, rapid weight loss, sore lower back due to swollen lymph nodes. again, sorry as I don't mean to uneccessarily frighten you. But, you can never be too careful.

Your body fat percentage is not unusual for a trained athelte. the fact you aren't training as much and get infections easily means you should look into other sources of fat lose - like chronic infection, though overtraining can lead to a generalized immune response that can lead to health problems. the disc problem is something you need to see a doc about!

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"My strategy is to start out slow and then peter-out altogether" Walt Stack

This is an interesting problem. Any number of factors, either exclusively or in some combination, may be contributing to this. Perhaps the more ugent issue is recurrent colds. To me, this indicates the need for a thorough physical including comprehensive blood work. Be certain to tell the physician you are an endurance athlete and give him a detailed history. Adipose tissue (fat) is an important physiological component. You need it for a variety of critical functions. When the percentage of adipose tissue for your body frame falls below adequate levels there is likely to be some physiological adaptations that take place or try to take place. The symptoms you're describing could be indicative of that, or of something less acute and more chronic. Either way, this needs to be professionally diagnosed, not by an armchair poser like myself. Call the doctor.

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Tom Demerly
The Tri Shop.com

5'11" at 154 lbs hoovering around 6% BF.. I've always been pretty thin, prior to the tri-training I was 168 lbs. If anything my immune systems seems to have taken a serious kick in the ass.. I haven't been sick in over 9 months (gonna jinx myself).. as already mentioned, it could be something completely unrelated to BF.

mike

Please do call the doctor, and let us know what he or she says. Women do not function properly at such low levels of BF, but men certainly can and do. Mark Allen said at a talk I heard him give, that even at 4% (for men, presumably), one would have enough fat to provide fuel to run (slowly) from San Francisco to San Diego, without any extra nutrition. He was surely speaking hypothetically, since at 3-4%, about all that's left is what surrounds the internal organs, and they don't give up their cushion easily nor should they. But his point was about efficiently training the body to burn fat first as a fuel source under aerobic load. I thought it was an interesting visual.

ken, i'm 5'11 and 150 lbs. i've got about 5% or less body fat. i'v haven't had any health problems associated with that. i very rarely get sick. i would look at your diet carefully, as well as have some blood tests done. I'm vegetarian and often times us veggies have low iron which does bring your immune down. i would get blood tests done first, if that shows nothing abnormal, maybe consult a nutritionist with some experience with athletes. take care of it soon though. .......luke.........

I agree-- your symptoms are somewhat scary. Get checked out by doctor, asap. Full blood work etc.

While your symptoms (sudden weight loss, back pain and recurrent colds with fever) may be due to overstress of some kind, they certainly could be something much more serious!

Good luck at the doctor's and may it all turn out to be nothing serious!

Ziva

Like Luke I can achieve a low BF% (right now 6'3" 195# and 4%, based on a 3 site test with lange calipers). I am usually the only one in the house that does NOT get sick (hard to do with a 2 year old germ catcher running around). Perhaps people like Luke and myself are more accustom to it?

I think you need to find out why you went lower. I weigh everything I eat, can tell you exactly how many calories burned in a workout, can tell you my basal metabolic rate for a given BF %, and know every calorie that I ingest. I even have the macro and micro nutrient breakdowns (can anyone say anal-retentive). So when my weigh fluctuates or I feel tired or my workout sucks, I can look at my spreadsheets and tell you why.

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Ross Hoopingarner

One more thing to add. A lot of people will say, you need to get to a doctor if your bodyfat is that low. I have done a lot of research and asking, no one to date has been able to provide me the burden of proof that it is bad for a male.

The only thing I would be concerned with is if you achieved it very quickly for no apparent reason, it should not be something that should come easy to most people.

But if like me you train 20hr/week and you eat a balanced diet, take your vitamins, something has too give.

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Ross Hoopingarner

Has your overall caloric intake changed during this time period? Have you been getting enough essential fats (ie flax, fish, etc). Low BF (within limits) should not be a problem provided you are providing your body with what it needs. Most often people cut there fat intake back which can cause problems with the immune system, inflammation, all sorts of things.

Also, when the body is under stress like that caused by a bad lower back (disk) all sorts of systems can be blown out of whack. It would seem that the pain may have caused you to train differently possibly losing some lean tissue along the way.

I agree with everyone else that you should seek a doctors advice.

I guess I hit send too soon. I also need to add one more bit of information (I've been flamed on this subjuct many a time on other forums, so I need to clarify one bit of info)

Low bodyfat in males can be the symptom of something more serious, hence the reason I am concerned if someones bodyfat drops suddenly for no apparent reason. However, I have seen no proof that low bodyfat in males brought on by an extreme exercise/nutrition regime has caused something more serious than perhaps fatigue or under performance.

OK, I'm done -- Flame Away.

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Ross Hoopingarner

T2 absolutely right, people that achieve lower BFs by cutting away too much fat typically show a greater incident of normal sickness (i.e. colds, flus, etc.)

I eat 100-200g of fat in the form of flaxseed oil, animal fats, soy, etc. daily.

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Ross Hoopingarner

I normally race around 188 and 10% during the season. This off-season (Oct-Jan) I usually go up to aorund 195 lbs. Then the beginning of the year I start eating better and my weight comes down by April or so to a comfortable weight. This year I FLEW down and the trend has continued albeit slower now. I take a multi-vitamin and an essential fatty acid capsule everynight before bed. I also have been taking a different fat the last month or so called CLA (Conjugated Linoliec Acid)(could that be the cause)??? I have an appointment with my doc tomorrow afternoon. Goiong to have her check my Iron levels and search for any other cause. I do have a 20 month old daughter that goes to the Gym Daycare several days a week with my wife, I am sure that is a germ habitation, but it has never caused me problem in the past. Thanks everyone for your input. I think my diet has everything I need. I eat very little red meat, but I do eat plenty of beans and green leefy veggies. I eat nutritious cereals and skim milk, whole grain breads, etc.... And I eat around 3000-3500 calories a day. I train about 10-14 hours a week and sleep anywhere from 6 to 9 hours a night depending on what is going on that night or the next morning. Am I just being a hypochondriac(sp)??

I'm with you Hoop. I detail my eating habits similiar to yours and look at fluctuations in body weight very closely to determine what it the cause. Also, like you, I consume around 30-35% of my calories from fat sources like those you mentioned. Fats support a healthy immune system and reduce inflammation which are two things any endurance athlete surely wants.

The testing on CLA was sketchy at best, but many swear by it.

Do you have any logs of how that weigh came off last year? Is your volume up in relation to your cal intake? Intensity up?

It sounds like you are just more in tune with the details this year and the differnece is actuall intake vs. output. People never realize how much they cheat on a diet until I make them write it all down. Even as anal as I am, I still 'cheat' about 5-10% of the time on my diet (triaining for IM allows a lot of wiggle room in the diet) but others around me would insist that I never cheat.

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Ross Hoopingarner

Weight has come off pretty simlar to the last couple years. Just went further this time. My volume is actually down by 6 or 7 hours as compared to last year. ANd being still in BASE the intensity is still pretty low. I am actually eating much better this year, much less likely to veer off the diet plan so that may explain the difference in weight loss this year.

I think I might just stop the CLA just to see if that is causing some sort of problem. I am not quite to the anal point you are buddy!! but I still keep track of things:)

I'm reaching back to some dark corner in my mind from when I was getting my exercise science degree, but I'd be willing to bet that essential body fat for males is 3-4%. Lower than that and you run health risks including colds, fatigue and suppressed immune system function. I remember when I was at 4% (hydrostatic) BF a 2:00 Oly tri was really really tiring. I'd run out of energy near the 5k mark. 5% BF and 1:57-8 was the norm.

As for your back I'd be at the docs in 3 minutes at most. I did back rehab for 5 years and you DO NOT want to f*ck around with a back injury. One ruptured disk and you can kiss at least the rest of this season goodbye. I'd make sure the doc looked at your back and/or referred to a specialist if there are complications in addition to getting some labs drawn.

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

". . .And I eat around 3000-3500 calories a day. . ."

For a 6'4" guy who weighs 180 LBS and exercises 10-14 hours a week, 3000 to 3500 calories a day is not enough to compensate for your training load.

For example, I estimate your base metabolic rate is 2700 calories per day, assuming 7 hours sleep and 17 hours awake with normal activity levels (1 cal/KG/hr sleeping, 1.5 cal/kg/hour awake).

Running 8 minute miles burns another 13.2 calories/hour/hour or 1082 calories per hour.

This means you need 3782 calories on days when you run one hour and 4829 calories when you run 2 hours. It looks like you are running a caloric deficit of 700 to 1300 calories per day. Each 3500 caloric deficit works out to a pound of weight lost, so your deficit would cause you to lose 1.4 to 2.6 pounds a week. This is on the high side for desirable weight loss rates could be a contributing factor. I'm not implying that you shouldn't see a doctor, but you will need to eat more if you want to maintain your weight.

-Marc

I think your BMR is off. Using the Harris Benedict method I get 2010 and with the Katch-McArdle Method I get 1957. So at worst by your calcs he's over by 600/day. Either way, it's still probably low, when I run 2hr+ or cycle 4hr+ I'm usually in the 5000-6000 range. I average in the low 4000s and when I'm on a 20hr week I dont hold back if Im feeling extra tired or hungry, I still make sure to count the cals and take my BF measurements regularly just to be able to go back a compare.

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Ross Hoopingarner

Thanks for the feedback, Hoop. I had used guidelines from memory based on Janssen's Lactate Threshold Training book for my original post. I just applied the full Lactate Threshold Training caloric expenditure guidelines and I got a BMR of 2654 and an exercise energy expenditure of 775 cal/hr for running ~7:30 miles for a total requirement of 4205 calories. That is a bit less than I earlier posted but still represents a significant deficit.

I understand that there are many methods and that they all give conflicting results. The best way to know individual numbers is for an individual to carefully measure his own activity, eating, and weight and use it to determine his unique energy needs.

What's interesting is that Ken dropped about 11 lbs since he started training this season. You could look at the difference between his weight when he started training and his current weight, divide it by the number of days he has been in training, and multiply by 3500 to get another data point for his average daily caloric deficit. For example, if he dropped 11 lbs in 70 days of training, his average daily caloric deficit would be 550 (11*3500/70).

-Marc

I just read a subsequent post from Ken where he mentioned he got up to 195 lbs in December-January. If Ken dropped from 195 lbs on January 16 to 177 lbs today, that comes to a deficit of 900 calories per day!

Maintaining that kind of a caloric defecit is stressful, even if he is maintaining minimal body fat levels.

I think this is a case of a stallion who is eating like a pony.

-MK

Funny body fat story. My work had a health fare yesterday where one of the things they did was measure body fat. Coworkers were taking bets on how low I would go (6' 0" 145 lbs). Four tries with a hand held measurement device and they still couldn't get a reading (machine only goes down to 6% supposively)!!!

Seriously though, I'm a little uncomfortable in the pool when the covers weren't on the night before.