One of the issues with this question is that health and fitness is a lifelong commitment and while your goal may have a specific deadline (e.g. the summer), maintaining the results of your hard work will require long-term commitment.
If you are prepared to commit yourself to an exercise program, several factors come into play in determining when you will achieve your goals:
- How often are you exercising? Depending on your goal and your deadline, you may need to commit to a program that has you exercising several times a week or more.
- How intense is your training? Your willingness to push your body to the required threshold is another important factor. Being physically active is great but if your goal is to improve upon something (i.e. strength, weight, etc.) you will need to meet the appropriate intensity level to reach your goal.
- Are you able to stick to a meal/diet plan? Your ability to modify and stick to the right meal plan is important if your goals are related to strength gains, weight loss, weight maintenance, etc.
- Is your goal attainable? Perhaps most importantly, are your goals realistic and attainable when compared to your lifestyle and your genes? Setting a goal that you are unlikely to achieve can be demoralizing and counterproductive.
You may see and feel changes after a few days, weeks or months, but it could take longer to reach your goals. The first step in any case is just to get started!