Interesting Answers From BistroMD Dietitian
When I had family visiting and ate off plan for 7 days.. the next week I dropped 4 1/2 lbs what happened
Before I address the set point theory and how to affect that, let me first address why it is that you ate “off track” while visiting with family and then lost so much the next week.
What happens to your body after eating the same amount of food consistently for 4-5 weeks is it kind of hits a plateau. Basically your body gets used to what you are providing it and doesn’t work as efficiently for you. In Dr. Cederquist’s medical practice it’s at this time that we introduce what we call a “metabolic adjustment” phase. What this is is increasing the amount of calories you eat for 1-2 weeks (typically by adding in more lean protein, fruit and veggies, but pizza works too 
). What this does is bumps your metabolism up and gets your body looking at different foods. Then the week after the adjustment you cut back down on the calories and your metabolism is still “revved” up so you can burn the calories more efficiently. So basically that is what you did for those 7 days. You gave your body something different to look at.
Even with our program, I recommend that every 4-5 weeks you add in a little bit more to your plan (another protein snack, a piece of fruit and maybe a salad with dinner) for a week or two to rev up your metabolism, then bring the calories back down.
How to affect your Set Point
As for the set point theory, the set point is the weight range in which your body is programmed to weigh and will fight to maintain that weight. Some believe that the number of fat cells the body contains at the end of the first year of life determines the set point. The amount you eat, the fat content of the diet, and the level of physical activity determine how large those fat cells will become, and how heavy you will be. This means that no matter how many fat cells you have it is possible to shrink the amount of fat storage they contain, although, you need to select the correct exercise and diet suited to your needs.
Unfortunately, most research says that the real only way to change your set point is by exercise. Water aerobics is a great thing. Low impact and great resistance. If you can increase the number of minutes in the pool by even 2-3 more minutes each time you go, that would be helpful.
Again, the best way to affect your set point is by exercise but also by not restricting your caloric intake too much and just eating a healthy well balanced diet.
