Best, worst of times for Erica Hill's health goals

CBS News Medical Correspondent Dr. Jennifer Ashton is giving "Early Show" co-anchor Erica Hill, as well as viewers, health tips as Erica spends six weeks trying to squeeze healthier habits into her hectic days. Dr. Ashton is blogging about her observations of Erica's efforts.

WEEK TWO: Best and worst of times for Erica's efforts

For anyone attempting to improve their behavior from a health perspective, the first few weeks can be both the easiest and the hardest. Usually, one's enthusiasm and motivation are at their peak in the beginning, which is definitely a good thing! But the changes that we sometimes want to see can take several weeks to months to really be apparent.

Since Erica is quite healthy at the start of her experiment, the fine-tuning she is doing by modifying her exercise program, her sleep routines, and her diet may take a little longer before really declaring themselves.

In general, fitness levels can take 4-5 weeks to improve. For someone who is sleep-deprived to feel more rested takes weeks of getting consistently good sleep. Sleep is probably Erica's biggest challenge, since she is breastfeeding her baby at night. And lastly, for someone with vitamin deficiencies to begin to normalize can take a minimum of 4 weeks in many cases. Erica has been supplementing her vitamin D3 and B complex intake for 2 weeks now, and we plan to recheck these levels in another 3 weeks or so.

She gets an A for effort on all fronts, so far! Go Erica!