Staying healthy and fit , or achieving the 'healthy and fit 'status , requires careful monitoring of your diet as well as your exercise routines. If I get your question right , you are planning to continue with your regular diet
( and water ) for the first two weeks , thereafter exercise , diet and water for the next two weeks .
This should be a good experiment for you to know what exercise does to you.
My suggestions to you would be
1. chalk out a systematic exercise plan ,after consulting an exercise specialist / physiotherapist , so that you perform the type of exercise which will suit your body the best and also, so that you stick to it . Too much exercise or too little exercise will just not give you the results you are seeking and in fact will demotivate you from continuing further.
2. If it is the first ever time that you are exercising , make sure you have the go ahead from a physician and to rule out any health issues that may interfere with your exercise routine .
Remember , any kind of exercise program goes hand in hand with your diet. So whatever be your goal , may it be
weight loss or fitness, a healthy nutritious is essential along with the right kind of exercises to achieve best results.
3. it will also help to consult a dietician for diet advice.