It takes an average of 66 days to develop a habit that you stick with, according to a July 2009 study published in the European Journal of Social Psychology. Some are able to form a habit in as little as 18 days, while others may need 254 days to make a behavior concrete.

No one ever said that changing your lifestyle would be easy. In fact, it may be one of the most difficult commitments you have ever made in your life. However, considering that you can change a bad habit that has been formed over many years, or even decades, in two months is quite impressive. It’s similar to cleaning your house. It took a week for the floor to get dirty, leftover food to pile up in the refrigerator and for dirty clothes to overflow your hamper. Those few hours on a Saturday morning are no fun as you clean up, but by noon your house is peachy clean. The reset button has been pushed.

Beginning and maintaining a diet and exercise program is challenging, but as your habits develop, you will gravitate towards the gym and the “heart healthy” food line. According to the study, the most significant changes happen early on in your behavior changing process, and tend to level off as your new diet or exercise change becomes a habit. Although individuals vary, here is what to expect when you begin a diet and exercise program:

First 2 Weeks- Breaking the Mold

Diet: As you begin to introduce fruits, vegetables, legumes, whole wheat products, lean meats and low-fat dairy into your diet, your body will resist almost every initial change. You may have diarrhea or constipation from your increased fiber intake from fruits, vegetables, legumes and whole wheat products. Foods high in fat and sugar will look “extra good” as you past them in the cafeteria or grocery store aisles. Your stomach may “cuss you out from the inside” as you reduce your portion sizes to a saucer-sized plate. Detoxing from alcohol or drug abuse has similar effects to detoxing from poor eating habits. The reward centers in your brain are craving those foods and resisting change.

The Good News: These feeling are temporary and will improve with each healthy decision you make. In addition, you will notice weight loss, increased energy, better mood and increased self-confidence. Continue to push, things get bettter.

Exercise: Your initial workouts will frustrate you. Your muscles will feel weak and burn. You will also begin to realize how weak you really are, and a 500 rep workout will seem impossible. Towards the end of your second day after beginning your exercise program, you will be sore. Getting out of bed, or walking up stairs will be miserable. You are not likely to notice an increase in muscle within the first two weeks.

The Good News: Soreness is the first sign of improving muscle strength! When you exercise, muscles are damaged and breakdown, which is your source of soreness. Over the next few days, your body will repair muscle fibers and improve nerve to muscle connections, which result in an immediate increase in strength. So, you will actually notice stronger muscles within the first two weeks, although your muscles may not become larger initially.

Second 2 Weeks- Initial Rewards

Diet: The second two weeks are the most rewarding in making dietary changes. After you body has detoxed, you will actually prefer smaller portions of healthier foods. You will wonder how you were ever able to eat a foot-long sandwich… With chips and a drink. The challenge here is to avoid becoming over confident. You may begin to experience boredom with healthier food choices. This is the point where you should begin researching “healthy foods that taste good” or “ways to make healthy foods tastier.”

The Good News: At this point you will notice fat loss. Your clothes may begin to feel slightly larger, and you will feel lighter on your feet. Healthy choices become “cool” and you are now a role model for both your family, friends and co-workers. Do not let those who are not supportive of your new lifestyle changes discourage you. They are jealous.

Exercise: You are doing well with your workouts, but other life commitments will appear more important. Planning and scheduling is important in this phase of habit formation. Set aside those 20-30 minutes every day to lift weights or perform cardiovascular exercise. Do not let anything, I mean ANYTHING, take this time away from you!

The Good News: Here, you will begin to notice positive changes in muscle growth and endurance. Take the time to appreciate how well your body rewards you for your efforts. Continue to push yourself through your workouts.

The Second Month- Finalizing Your Change

Diet: Maintenance and avoiding temptation is the challenge here. You made significant strides in developing new dieting habits during your first month. A small plate is the norm. You include fruits or vegetables in every meal. Keep this up! This is how you are supposed to eat. This is your new relationship with food. Those fatty and high calorie foods will tempt you. It’s like the old fling wanting you back. They keep calling and texting you to give them a second chance. Don’t. You are now dating (or eating, I guess…) “marriage material.”

The Good News: You may be halfway towards developing a lifelong habit. Make choosing your meals a “big deal!” You are no longer a passive eater. Each healthy choice you make will reward you with weight loss, a healthy heart, more energy, a reduced risk of cancer and better blood sugar control.

Exercise: You must continue to push yourself with your exercise regimens. Challenge yourself with more difficult workouts, such as the Tick Tock Challenge Workout. Instead of walking, try speed walking or jogging. Try exercises that you never thought you could do! No matter what, do everything you can to get your 30 minutes per day of exercise this second month. If you do, it will be a habit.

The Good News: Now you are in the “athletic body type” classification. How does that feel! Your knees and back are no longer achy. You can hang with your children of grandchildren without tapping out early. You are becoming the model of health for your family and community. Keep it up.

Congratulations. You have become a new person.