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The Feedzone with Monique Ryan: Rapid weight loss and your immune system

Published: Feb. 7, 2007

Dear Monique:
I have read your column in VeloNews for a while and have bothenjoyed and appreciated the knowledge. I have a questions about weightloss and it’s effect on the immune system.For the past few years I have been competing in the sport of triathlon.This year I decided to race bikes for the first six months. I knew thatbecause of the importance of the power to weight ratio, I would need tolose both “after season” weight from last year and some additional bodyfat to be competitive in the climbs.I set out to lose most of the weight (was 180 lb.) during the first12 weeks. I wrote down everything that I ate so that my caloric intakewas almost always lower than the expenditure by at least 500 calories (moreon the five hour ride days). I tried to eat balanced meals and smart snacks.I never had a workout where I felt carb-depleted. My question is, I caughta cold earlier this winter and had some symptoms for over three weeks.When I first felt sick I weighed about 163 lb. or so, but my scale (set-upcorrectly) said that I was still 16.5-percent body fat.Is there evidence that weight loss affects the immune system? I knowthat the workouts I was doing could, but in your opinion is there a synergisticeffect?
Thanks,
JBDear JB,
As you clearly understand, your immune system is affected by a numberof factors related to training, nutrition, and lifestyle. More specificallyyou want to know if weight loss is a separate risk for compromising yourimmune system. It is a good question, as many cyclists focus on body compositionchanges and weight loss at this time of year. It appears that you achieveda weight loss of 17 lbs. in about a twelve-week period, which is more thanone pound weekly. This is considered a fairly rapid weight loss rate duringa cycle of training in which you are completing long distance workouts,such as the five-hour bike rides that you mentioned. In addition, it appearsthat some of your weight loss could possible have been loss of muscle tissue,if your body fat levels did not lower to the level that you had expected.There is limited data on the effect of rapid weight loss in athletes,though this has been studied in overweight women.  “In these non-athleteswe found that with a weight loss of 1.5 weekly, which was a deficit of750 calories daily, there was a decrease in T-cell function,” accordingDavid Nieman, PhD, researcher at Appalachian State University. Becauseof this negative effect on the immune system, it is recommended that cyclistlose weight at a rate of one-half to no more than one pound weekly. A drop-offin training from due to illness may not be worth the accelerated weightloss effort.In addition to the calorie restriction that this rate of weight lossrepresents, it may also represent other nutritional inadequacies. Virtuallyall nutrients in our diet play some sort of role in keeping our immunesystem healthy. “Our immune system is heavily dependent on glucose andthe amino acid glutamine,” said Dr. Nieman. “When the carbohydrate andamino acid supply is down our immune system can be compromised.”Even if you paid attention to consuming carbohydrate during hard workouts,particularly those long training rides, you may not have been consumingenough for adequate recovery because of your accelerated weight loss efforts.By cutting back at least 500 calories daily, it is assumed that some ofthese calories came from carbohydrate and protein sources, which couldhave compromised your daily glycogen repletion and recovery from one trainingsession to the next. Several studies have looked at the impact of dietarycarbohydrate on hormonal and immune response to exercise. When exerciseis completed over several days time on a low carbohydrate diet the magnitudeto which stress hormones respond to exercise is much higher than with adiet adequate in carbohydrate. While these experimental diets were verylow in carbohydrate, it is assumed that athletes who are carbohydrate deficientin their daily diet are placing themselves at risk from the known immunosuppressiveeffects of hormones such as cortisol. Keep in mind that the amount of carbohydratethat you require on a daily basis is related to the duration and intensityof your training sessions. In addition to your carbohydrate status, yourdieting could also have compromised your protein status, particularly ifyour weight loss efforts resulted in the loss of lean body mass.It is good that you brought up the point of not completing workoutsin a carbohydrate depleted state, at it may help other cyclists appreciatethe risks of not replacing carbohydrates during training. While your muscleglycogen stores may not have been optimal at the start of certain trainingsessions, I am assuming that you are referring to your carbohydrate intakeduring training.Because much of the immune function impairment related to exercise ismainly from an elevated concentration of stress hormones, one of the nutritionalstrategies that could effectively reduce this stress hormone response toexercise is the effect of carbohydrate consumption during training. Severalstudies indicate that consuming carbohydrate during exercise does a betterjob of maintaining blood glucose levels during exercise, and that thisweakens the usual rise in stress hormones such as cortisol, results inless dysfunction of the immune system, and in less inflammation. “We arenow analyzing data in which cyclists trained for three hours at 65- to67-percent VO2 max, and comparing carbohydrate intake duringthis exercise to a placebo. What we have found is that parts of the immunesystem show less dysfunction and less inflammation with the carbohydrateconsumption,” said Dr. Nieman. “We still need to determine if this translatesinto less infection.”When you are on a calorie restricted diet in an attempt to lose weight,you can also compromise your vitamin and mineral intake. Though true deficienciesare not common, insufficient intake could affect your resistance to infection.So, it is best to eat a balanced diet of high quality foods to keep vitaminand mineral stores in the body at optimal levels. If you do supplement,keep to modest doses, as excesses of some minerals such as iron and zinc,can impair immune function and increase your susceptibility to infection.For cyclists trying to improve their strength to weight ratio, it isbest to approach any type of weight loss, or body fat loss slowly. Thisprevents nutrient deficiencies and should keep your immune system stronger.Good luck,
Monique


Monique Ryan, MS, RD, LDN is a nationally recognized nutritionistwith over twenty-two years of experience and is owner of Personal NutritionDesigns, a Chicago based nutrition consulting company that provides nutritionprograms for endurance athletes across North America (www.moniqueryan.com).Monique consults with the Chicago Fire Soccer Team, and was the nutritionistfor Saturn Cycling from 1994 to 2000. She has also consulted with the Volvo-CannondaleMountain Bike Team, the Gary Fisher Mountain Bike Team, and the RollerbladeRacing Team. Monique has consulted with USA Cycling, and was a member ofthe Performance Enhancement Team for the Women’s Road Team leading to the2004 Athens Olympics. She has also provided nutrition consultation servicesto USA Triathlon for coaching clinics, athlete clinics, and for the residentathlete team and was a member of the USAT Performance Enhancement Teamfor the 2004 Athens Olympics. Monique is the author of "SportsNutrition for Endurance Athletes," 2nd edition (March 2007), from VeloPress,which provides sports specific nutrition for road cycling, mountain biking,running, triathlon, swimming, rowing, and adventure racing. She is alsoauthor of "PerformanceNutrition for Winter Sports" (PeakSports Press), "Performance Nutritionfor Team Sports" (PeakSports Press), and "Complete Guide to Sports Nutrition."Monique is a regular contributor to VeloNews, Inside Triathlon,Outside, and ACE Fitness Matters. As part of the FeedZonecolumn, Monique will answer selected questions online. Please sendyour questions to RyanWebQA@aol.com.