Even trainers get sick. Yes, we are not invincible! The one downfall to training for a competition, believe it or not is lower immunity. Once your body falls below 18.5% body fat, you have lower immunity and you can become sick easier. This is why I would never do this more then once in my life because staying within a low body fat range can also cause other irreversible effects.
-Low Immunity: as discussed above;
-Cancer Risks: people that do not get enough healthy fats and are malnourished Fall prey to types of cancer. Vegetables and fruits help your body protect against cancers.
-Osteoporosis, Bone breaks and Fractures: proper nutrition and healthy fats promote healthy bone growth. Proper vitamins and minerals from your food help decrease your chances of developing arthritis,brittle bones and osteoporosis.
Please make sure to hire a professional that really knows what they are doing and are taking your health into consideration, not their "image" as a trainer.