First lets talk about Leptin.
Leptin is secreated from your fat cells as fat makes leptin. A fat cell inflates and deflates with fat loss or gain and the more fat that is lost in the cell the more leptin is reduced, conversely the more fat that is in the cell the more leptin is produced. There is a point where fat cells like to maintain and at that point the amount of leptin your cells secreate is optimal so drivers to eat and energy expenditure should be balanced.
However, when we are in a fat loss phase, leptin is reduced and can take affect from the very first day of dieting. This affects your drive to eat as it communicates energy availability to the brain. It also influences your thyroid hormone responsible for your basal metabolic rate to the large part and your SNS (sympathetic nervous system) influencing basal muscle tone, things like fidgetting are altered and a feeling of lethargy may be apparent therefore reducing overall NEAT (your general movement throughout the day)
Fat loss is not the only reason why leptin reduces. Leptin decreases due to calorie restriction and the available glucose we have at our disposale in the body as it is now being used for your bodies daily functions and not stored as gycogen and exercise preformance e.t.c...
Glucose feeds into the HB pathway, this converts some of the glucose into acetylglucoseamine which leads to leptin secretion.
This tells us that glucose availability and acute calorie balance is a big part of leptin secretion and why a person will experience hunger quite early on into a diet.
However there is a solution-
Adaption can happen within the first two weeks of a diet but depends on the size of the calorie deficit (the bigger the deficit the quicker the adaption and leptin lowering response)
When eating at maintenance for (24-48 hrs) within a short term diet, leptin levels can normalise.
For longer term diets leptin takes around 1-2 weeks to return to normal
This should be at maintenance or just above and primarily with carbohydrates, even a tiny deficit will not have a positive affect on increasing leptin levels.
Here are the suggested diet break frequencies for men and women according to thier body fat percentage-
BODY FAT % DIET PERIOD MAINTENANCE PERIOD
MEN 20%+ 12-16 weeks 1-2 weeks
WOMEN 30%+ 12-16 weeks 1-2 weeks
MEN 15-20% 10-12 weeks 1-2 weeks
WOMEN 25-30% 10-12 weeks 1-2 weeks
MEN 12-15% 6-8 weeks 1-2 weeks
WOMEN 20-25% 6-8 weeks 1-2 weeks
MEN 10-12% 4-6 weeks 1-2 weeks
WOMEN 17-20% 4-6 weeks. 1-2 weeks
* The reason for the reduction in dieting time for the lower body fat percentage is the correlation between less body fat and therfor less leptin.
if you don't know your body fat percentage you can google images with examples of body fat percentages and compair to yours.
The PROS of this method -
Brings leptin levels back to normal and all the other affects associated
Its motivating and breaks up the diet
Allows you to get into the swing of eating at maintenance
Improves your energy, therefor your activity levels, training performance, and NEAT (normal daily movement)
Breaks up the boredom of one long diet
Can make weight loss take a little longer, however with the evidence of adherence and all the other benefits this is a great method to apply.
This method isn't really needed for a short diet but maybe have a couple of days at maintenance if required.
Other methods are the Matador diet which involves two weeks of fairly hard dieting and two weeks at maintenance then repeat
Or some prefer 2 days of hard dieting and 1 day at maintenance and repeat.
A note on refeeds and cheat days-
Refeeds involve eating at maintenance or slightly above for 4-24 hours within the diet phase.
The main reason for this is to help someone adhere to their diet and to top up glycogen stores if training hard. It can help if someone is getting a bit de-motivated or on a fairly large deficit which doesn't allow for any indulgencies.
Cheat days are very different to refeeds. The word cheat immediately implies that this is bad and therefor already has a negative connotation attached to it. A cheat day can quickly get out of hand and can completely undo someones week of progress.
Overall the main purpose of a diet break/refeed is for behavioral and psychological benefits
with biological changes being incidental.