We've heard a few reports of headaches occurring after the first week of the healthy lifestyle challenge.

One possible cause could be the result of withdrawal from caffeine.
Caffeine headaches can go on for days and the only relief is – you guessed it – more caffeine. Light is suddenly too bright to bear, concentration is impossible, and all one wants is relief. Many people reach for some over-the-counter drug but whoops! They all contain caffeine.
So why do we get a headache when we skip our morning cuppa joe? Caffeine acts as a powerful vasoconstrictor in the brain. That is, it constricts blood vessels in the brain and decreases circulation. Oxygen to the brain can be decreased up to 30%! When caffeine is not present, the sudden increased circulation causes major headaches.
Of course, a well-oxygenated brain is what we want for optimal health. You can avoid caffeine withdrawal headaches by slowly weaning yourself off of caffeine.
You’ll need some rest
Often the headaches are accompanied by more caffeine withdrawal symptoms. Fatigue is the next most common experience people have quitting caffeine. If you’ve been depending on caffeine to keep you going day after day, your body is going to need some rest. Think of your adrenal glands as exhausted horses that have been whipped way too long. Take away the whip and they want to lie down in their tracks! Make time to get some rest especially in the beginning of weaning off of caffeine.
Waking up is possible without caffeine
Since caffeine artificially increases cortisol production, the hormone that makes you wake up in the morning, people going through caffeine withdrawal can experience a hard time waking up without coffee as a stimulant. Once your adrenal glands have readjusted to their natural rhythm of producing cortisol in the morning without a stimulant, you won’t need a cup of coffee to wake you up.
Get some help from supplements
Decreased alertness, brain fogginess, inability to concentrate and feelings of decreased well-being including irritability and depression are frequently experienced during caffeine withdrawal. Don’t worry, there are herbal and nutritional supplements that can aid your recovery and make the transition easier.
Some people report feeling flu-like symptoms, muscle pain and even vomiting. That’s why we don’t recommend going cold-turkey! We’ve seen too many people suffer needlessly when they trying caffeine withdrawal suddenly.
It will be easier than you think
While this caffeine withdrawal phenomenon keeps millions of people addicted to their coffee habit, the good news is that you can avoid this pitfall by slowly weaning yourself off caffeine over a two to three week period. Many former coffee drinkers report that they can’t believe how much energy they have once they recover from the caffeine-driven roller coaster ride!