I think it depends on how high the calories are for the 'free day'.
In your example, I wouldn't really call a 500 calorie increase over your normal calories a 'free day' exactly, at least in the meaning that it's often used in diet plans. When I read about what most people call 'free days', they're usually pig-out days, featuring huge quantities of 'forbidden foods'. In the typical free day scenario, people spend one day a week eating themselves silly and then go back to dieting for the other six days.
Bear with me while I talk about the whole 'free day' concept for a minute
and then I have a few comments about what you're doing (which BTW sounds fine to me
). Here's my entirely unscientific two cents - no, I don't think that taking a 'free day' will boost your metabolism. What it will do is boost your
calories for the week!
The reason for a free day being included in a diet plan is probably just to make it more marketable/more acceptable to Joe or Jane Average American, IMO.
The question is whether taking a free day is a more effective way to lose weight? At the end of the day, weight loss comes down to calories in versus calories burned (I know that's oversimplified and that the quality of the food matters a great deal also but calories
are the bottom line
). One pound of fat equals 3500 calories, so we have to create a 3500 calorie deficit in order to lose one pound of fat, either by decreasing calories in (what we eat) or increasing calories out (what we burn through exercise and normal activities).
OK - so let's say you eat 1500 calories a day for six days and then have a free day of 4000 calories (this isn't an exaggerated number - there are lots of people who have had 4000+ calorie free days that are perfectly 'legal' or 'on plan'). That person's total for the week is 13,000 calories. Divided by seven, it averages 1857 calories per day. For many of us, it would be difficult to lose much (if any weight) at that calorie level because it's not going to create very much of a calorie deficit.
Compare that to what you're talking about - six days at 1500 calories and one at 2000. Your total calories for the week would be 11,000 calories, or 1571 per day. That's a more reasonable calorie level for safe weight loss than in my example above - and it's more likely to create a calorie deficit since it's almost 300 fewer calories per day than my other example.
I'd call what you're doing with six 1500 calorie days and one 2000 calorie day more like 'calorie-cycling' or 'zigzagging' calories. That's a pretty well-established idea in dieting: taking a reasonable total of calories for the week and dividing them up
unevenly. Some people calorie cycle every three days; others cycle grams of carbs (which ends up cycling calories). The thought is, like you said, to keep your body guessing about what's coming and keep your metabolism from getting sluggish or too complacent. It's important to stick to healthy food even on your higher calorie day, IMO. An extra 500 calories of good food may help with weight loss, but I'm pretty sure that an extra 500 calories of junk food isn't going to be too effective for long-term success.
I have to say though, that I think the best way to boost metabolism AND burn fat (and create a calorie deficit) is with exercise! Cardio exercise burns calories; weightlifting builds muscle which burns calories and gives you a tight, toned look. Either way, you don't have to starve yourself in order to create a calorie deficit and lose weight.
Gosh, I kind of took your question and turned into a treatise about free days generally.
Sorry about that - I feel like the 'free day' concept can really de-rail people so I wanted to give my opinion. Bottom line - what you're describing sounds fine to me so long as those extra calories are the same kinds of foods that you eat on your other days.
Hope that helps!