How much do we know about refeeds and diet breaks?
We know that athletes, although not typically overweight or overfat, often pursue phases of weight loss for a variety of reasons. Common motives include reaching a target weight class, improving power to weight ratio and enhancing aesthetic appearance. Now athletes have a couple of options within their arsenal to achieve this – namely – nutritional adjustment, or activity adjustment. As athletes typically already have high exercise-activity energy expenditures, nutritional interventions are often applied. The most common method includes something called continuous energy restriction, where the athlete consumes less calories than expended, every day, for the duration of the weight loss phase. However, some research suggests that there could be a better way.
This new way refers to intermittent energy restriction, which acts as an umbrella term encompassing refeeds, diet breaks, cheat meals/days. Essentially this method of dieting involves the alternation of a period of caloric deficit, with a period of increased eating. Sometimes this is to a predetermined amount of eating (refeed/diet break), and sometimes it’s a period of unrestricted eating (cheat day/meal). These higher feeding periods can involve an overall increase in food intake, so increasing protein, fat and carbohydrate …. or it can involve an increase in certain macronutrients, for example giving preference to increasing carbohydrate intake. There’s also a lot of debate regarding how frequently refeed periods should be implemented. For example, some nutritionists and coaches suggest that refeeds/diet breaks should be implemented more regularly as the athlete approaches lower levels of body fat (when they are more susceptible to muscle losses), whereas others recommend a consistent refeed schedule such as a 1 week refeed following every 3 weeks of dieting. So, as you can work out, we don’t really have specific guidelines on how to structure intermittent diets just yet, or how to optimise them. This is largely because intermittent dieting is still very new from a research standpoint, and we just don’t have enough literature looking at different intermittent diet protocols, particularly in athlete populations.
Recently, I along with Dr Layne Norton, Dr Eric Helms, Dr Andy Galpin and Prof Paul Fournier decided to tackle the research on this topic to see if intermittent dieting really has a place in athlete weight loss interventions. Our research showed us that athletes are already using intermittent diets despite a lack of supporting evidence, with particular adoption in physique sports, and now gaining traction in combat sports. The rationale behind intermittent dieting is that by implementing refeed periods or temporary periods of increased eating during the diet, one can offset some of the negative adaptive responses to energy restriction, namely reductions in energy expenditure and increases in appetite. In other words, refeeds might provide a metabolic boost or jumpstart that allows dieting efforts to be more efficient, and suppress the drive to eat allowing better adherence. It’s also suggested that refeed periods may replenish muscle glycogen stores, subsequently preventing an athlete’s performance from becoming negatively impacted as they lose weight. It’s also possible that if an athlete is able to better maintain their training volumes via a temporary boost in energy/calories, that they will then perform better during competition, and lose less muscle in the dieting process.
Now based on that rationale you might think that intermittent diets sound so much better than a standard continuous diet. But to be honest, we actually don’t really know yet. There have been a lot of positive anecdotal reports among athletes and coaches who have strongly advocated for the use of intermittent diets and have vouched for their efficacy. But, even though the use of intermittent diets and refeeds is very prevalent in the fitness community and in many sports, we only have two scientific trials that have actually compared an intermittent diet with a continuous diet in athletes (one yet to be published). It’s quite funny, because intermittent diets are sometimes seen as this advanced scientific practice, but at this stage it’s mostly based on theoretical principles and anecdote, we don’t really have the data yet.
So, what are the key takeaways from the current body of intermittent vs continuous dieting research. We have some evidence that intermittent diets could be superior to continuous diets, with most of these studies on overweight people. Nonetheless, if I was an athlete beginning a weight loss phase, I think a diet with refeeds/diet breaks is a reasonable alternative to traditional continuous dieting. We can’t confidently say that this type of intermittent diet would outperform a continuous diet, but we have no data to suggest that the intermittent diet would be worse in any way. I think in an absolute worst-case scenario an intermittent diet might provide equal fat loss and muscle retention compared to a continuous diet, but could provide a unique psychological benefit by giving the athlete a little mental break from dieting, which could potentially improve the athlete’s mood state and adherence to the program. In the next year or so as we publish findings from my ICECAP trial, we should be able to speak more confidently in terms of whether or not intermittent diets are indeed better than your traditional continuous diet for athletes.
As a final discussion, I am going to make some practical recommendations for an athlete considering an intermittent diet based on our recent review of the literature. It’s important to remember that some of these recommendations would also apply to a continuous diet.
- Avoid rapid weight loss. Severe dieting may cause greater lean mass losses than moderate dieting, particularly in lean athletes. Too severe of a deficit may also adversely affect health and performance outcomes including reduced muscle strength, glycogen stores and reflexes, and increase the risk of injury due to fatigue. It would be practicable for an athlete to adopt a moderate level of restriction that encourages absolute body weight losses of 0.5% to 1% per week. Alternatively, an athlete may elect to reduce energy intake by a maximum of 35% relative to energy requirements for weight maintenance.
- Resistance exercise. Athletes implementing an intermittent diet should be encouraged to partake in regimented resistance exercise as a means to attenuate lean mass losses. Greater retention of lean tissue will likely minimise performance decrement during the diet and may lead to greater fat loss efficiency.
- Duration and ratios of dieting and refeeds. With the limited human research available, a conservative practical recommendation is to alternate 2 weeks of moderate dieting with 2 weeks in caloric maintenance. Currently it’s unknown whether this manipulation of energy intake is ideal for maximal fat loss and lean mass retention, or if additional arrangements may be superior.
- Coordinating refeed periods. It may be advantageous to synchronise intervals of caloric maintenance with outcome-focused or high-volume training periods. This tactic may allow the athlete to perform optimally during training sessions by providing additional nutritional support and negating the adverse consequences of a sustained, daily caloric deficit.
- High protein intake. High protein intakes may be beneficial to an athlete during dieting by reducing lean mass losses, providing greater satiety and increasing energy expenditure through the thermic effect of feeding. A daily protein intake range between 2.3-3.1 g/kg of lean body mass (which equates to approximately 2.0-2.6 g per kg of absolute body mass for an 80-kg athlete with 15% body fat) is likely an appropriate practical recommendation for athletes undergoing an intermittent diet with concurrent resistance exercise.
- Emphasizing carbohydrate intake during refeeds. Although yet to be confirmed, it seems wise to place emphasis on increasing intake of carbohydrate during refeed periods opposed to increasing protein or fat. Elevated levels of leptin following carbohydrate feeding may cause stimulatory effects on energy expenditure and suppress appetite, leading to greater fat loss efficiency, and easier diet adherence. Greater carbohydrate availability during refeed periods may also result in more pronounced anabolic responses when the diet phase is applied in concert with resistance exercise, potentially reducing lean mass losses.
For more reading on this topic, and a comprehensive analysis of the intermittent versus continuous dieting research we direct the reader to the following review that you can access for free HERE.
If you want to see Jackson present his latest findings on intermittent energy restriction, he will be lecturing in Perth on the 23rd of March at the Optimising Body Composition Seminar.
(1) Peos, J.J.; Norton, L.E.; Helms, E.R.; Galpin, A.J.; Fournier, P. Intermittent Dieting: Theoretical Considerations for the Athlete. Sports 2019, 7, 22.