One major worldwide problem is the high incidence of obesity that has grown rapidly during recent decades. The current prevalence of obesity is estimated at approximately 400 million people worldwide [1].
In the simplest of terms, the main cause of obesity is an energy imbalance – eating more calories than expended per day.
The secondary drivers of this energy imbalance are a low resting metabolic rate, environmental factors, family behavior patterns, and poor food choices that do not induce an adequate satiety response [2].
Dietary interventions, especially low-calorie diets, have long been the primary treatment for obesity for decades. Consume less calories than you burn and the body will be forced to utilize stored body fat. Simple.
However, it is now known that “metabolic adaptation” exists during a dieting phase, whereby the body will lower its energy expenditure in other metabolic processes to compensate for the reduced energy intake.
This is thought to be an evolutionary adaptation that promotes survival. Such adaptations include a lower resting metabolic rate, thermic effect of food, and physical activity.
Maybe a more important factor to calorie-restricted diets is that they are not always realistic to maintain day in day out. Large meta-analyses on such methods demonstrate their ability to lose weight in the short-term, but weight loss tends to only be modest over prolonged periods as many people find it to be unsustainable [3].
The routine calorie restriction regimens always induce a quick weight loss at the beginning and seem to reach their best results after 6 months. However, this tends to be the timeframe in which weight loss stalls or digresses, hence why 30-35% of lost weight is regained during the 1st year after dieting [4].
Based on this, calorie cycling, also known as intermittent energy restriction, is a nutritional strategy that contrasts to the conventional approach of sustained calorie restriction by alternating periods of energy restriction with periods of greater energy intake. These non-dieting periods may often be referred to as “refeed” periods.
Calorie Cycling Benefits Vs. Continuous Caloric Restriction
Below we’ve listed all the science-backed benefits of calorie cycling, when compared to continuously restricting calorie intake:
Better Appetite Control
As mentioned, your body will try very hard to slow weight loss down, conserve energy, and even regain the weight after dieting. It is not within human nature to purposefully lose energy stores that may have previously been necessary for future survival.
One of the main ways the body will achieve this is through altering the production of weight-regulating hormones such as leptin (decreases hunger) and ghrelin (increases hunger) [5].
These chemical hormones are in constant communication with the brain to regulate psychological cravings and appetite for food.
If you lose weight, ghrelin production will increase, and if you add weight, leptin production will increase. This is an easy means by which the body can compensate for a change in energy intake and try to maintain some level of homeostasis.
This is backed by large scientific reviews that state “diet-induced weight loss results in long-term changes in appetite gut hormones, postulated to favor increased appetite and weight regain” [6].
To the point, by utilizing calorie cycling and infrequently increasing energy intake as part of a dietary break, there is potential to better control these appetite-hormones in the long-run to promote sustainable weight loss.
For example, many studies have concluded that brief refeeding periods during a weight loss phase can significantly upregulate leptin production whilst having no notable effect on stalling weight loss. In the long run, this is likely associated with reduced food intake and superior weight loss results [7] [8] [9].
This evidence therefore supports the potential inclusion of dietary breaks (1 day – 1 week) to provide better sustainability to a weight loss diet.
This counters the mindset of an “all or nothing” approach when it comes to weight loss, and actually utilising some degree of flexibility may be worthwhile.
Maintained Resting Metabolic Rate
Another issue with traditional dieting methods is that consistently reducing calories will eventually result in a reduced caloric expenditure per day. This is partly due to a reduction in the amount of calories burnt at complete rest for internal functioning, known as ones resting metabolic rate.
After 8 weeks of calorie-restricted dieting, it is estimated that the resting metabolic rate expenditure will be lowered by around 250 calories [10].
Studies that introduce some type of calorie cycling have shown some benefits to avoid this, or at least decrease the severity. Impressively, one study showed that calorie cycling was able to maintain resting metabolic rate whilst not affecting the rate of weight loss [11].
Such a result is not too surprising, as even in the health research there appears to be no difference between intermittent energy restriction and continuous energy restriction on certain disease risk factors [12].
This all provides good evidence that short-term diet cycling during a weight loss phase may be an effective way to promote more sustainable weight loss without associated reductions in resting energy expenditure [13].
Even competitive bodybuilders, whose sole job is to optimize their body composition, commonly report that the implementation of refeed days during pre-contest weight loss interventions has a positive effect on preventing further adaptive downgrades in energy expenditure – not to mention enhanced training performance and mental recovery [14].
May Avoid Other Side Effects
Although the main benefits of calorie cycling are improved appetite regulation and resting energy expenditure, there may be other notable inclusions to add to the list.
For example, long-term caloric restriction may also cause reduced testosterone production, decreased thyroid function, lower physical activity levels, and increased stress hormone release [15].
Despite no current studies having analyzed how calorie cycling might help to prevent these issues during a diet, it is speculated that it likely helps dampen the severity of these issues.
Considering long-term intermittent energy restriction and continuous energy restriction yield similar fat loss results [16], it may be worth trying calorie cycling if any of these factors have been problems in the past.
How to Implement Calorie Cycling
Calorie cycling is still a relatively broad term with no exact definition or definitive rules.
At this point all it means is that someone takes a short break in their weight loss diet to purposefully increase calorie intake, whether this is for 1 day or 1 week, before continuing with their diet.
The exact way that you choose to go about this is quite flexible and may depend on what suits your current lifestyle. There are not necessarily any right or wrongs.
The dietary approach that you can stick with best is going to be the one that works best for you.
In general, people will wait approximately 1-4 weeks before introducing a dietary refeed or break just to get the ball rolling.
After this period, and especially if someone notices a decrease in energy levels, physical performance, or libido, a dietary break may be introduced.
The specifics with the dietary break are flexible, but it is obviously ideal to be sensible and not go all-out with endless binges.
A good recommendation would be to stop dieting for 1-3 days and increase food intake by ~25% whilst enjoying some of your favorite foods that may be have been limited or avoided during a dieting phase.
After this time, the next dieting block can begin for another 1-4 week period.
Here are a few other calorie cycling protocols to consider:
- Weekend cycle: 5 days on a low-calorie diet, then a 2-day high-calorie refeed.
- Mini cycle: 11 days on a low-calorie diet followed by a 3-day high-calorie refeed.
- 3 on, 1 off: A 3-week low-calorie diet followed by a 5-7 day high-calorie refeed.
- Monthly cycle: 4-5 weeks on a low-calorie diet followed by a longer 10–14 day higher-calorie refeed.
Conclusion
Conventional dieting with consistently low energy intakes successfully leads to weight loss.
However, over time the body undergoes “metabolic adaptation” where it purposefully lowers energy expenditure to compensate for the reduced energy intake. It is also common for the body to try and increase energy intake by elevating hunger signals to the brain.
Recent evidence suggests that incorporating periods of increased calorie consumption during a dieting phase can negate, or reduce, these issues.
Further, dietary breaks or “refeeds” have shown to improve hormonal control and maintain resting metabolic rate during a weight loss phase, without incurring any negative effects on weight loss itself.
Those wishing to not only lose body fat, but maintain their results in the long run, may wish to utilize these benefits for a healthier and more sustainable result.