Intermittent energy restriction, also known as ‘non-linear dieting,’ can be defined as intermittent bouts of energy or calorie maintenance placed throughout the dieting period. The over-arching goal of this method of energy restriction is to mitigate the impact that metabolic adaptation, or “adaptive thermogenesis”, can have on the dieter and their progress over time.
Although, this dieting tool is not only exclusive to what we know as diet breaks, but to any sort of cycling done with our calorie intake over a day or weekly basis. Some other methods of intermittent energy restriction also include alternate-day fasting, intermittent fasting, time-restricted feeding, and refeed days.
What are refeed days, exactly?
Refeed days are what we think of as high carb days. We strategically increase our intake, mainly in the form of carbohydrate, for a time span of 1-3 consecutive days. The 1- to 3-day time span will vary depending on the individual, their level of leanness, time spent dieting, etc. to name a few.
Here’s an example: Say I’m dieting on 100 grams of carbohydrates, 150 grams of protein, and 45 grams of fat. My refeed day carbohydrate intake will fall somewhere around ~170 grams of carbs. This is approximately a 20% increase in total caloric intake (done via increasing carbohydrates alone), although this can also vary for the person and how well they may handle those additional carbohydrates.
With that said, it’s also important to mention that not everyone may need a refeed day. For a lot of people, the initial drop in food won’t be anything so low that refeed days will be necessary from the jump (assuming we’re starting this diet from a good place intake-wise). It may be more beneficial to adhere to the deficit on consecutive days/weeks until it becomes apparent that a refeed day can be helpful for the client (large dips in energy, training recovery, plateaus, etc).
Additionally, as we come to learn the client and how their body responds over time, we often notice how well (or not well) the client’s body will do with refeeds. Some may progress much smoother with a straight deficit through the week, while others will respond better by cycling their calories a few days at a time. Individual responses can vary immensely when it comes to implementing dieting strategies, so it’s not a one-size-fits-all here. It’s important to stay open-minded to experimenting with what feels and works best.
Onto the study
27 healthy, resistance-trained men and women completed this 7-week diet and resistance training protocol (58 were recruited initially). These subjects were split into 2 groups: a reduced calorie diet or an isocaloric non-linear diet. The isocaloric non-linear diet group, or the refeed group, followed 5 days of the reduced calorie diet followed by 2 days of maintenance calories (refeed days).
Diet and training measures
After being split into either a refeed or continuous dieting group, subjects were instructed to track their normal diets for 2 weeks in order to determine their maintenance caloric intakes. This is a great way to establish a baseline as opposed to equations or calculators, since individual needs and intakes can vary drastically between people due to many factors.
Once maintenance was found and the dieting/training period starting, all subjects were prescribed reduced-calorie diets with protein intakes set at 1.8 grams/kg body mass. As for the deficit itself, the continuous group was given a 25% reduction from maintenance calories to adhere to for the 7 weeks while the refeed group was prescribed a 35% reduction for 5 days out of the week (Monday-Friday) followed by 2 consecutive days at maintenance (Saturday-Sunday). The slightly larger deficit through the week in addition to the refeed days for the non-linear approach allowed the groups to follow isocaloric diets, or diets that are equated in calories. Refeed subjects were also told to increase their calories via carbohydrates only on refeed days. A great feature included here is that each subject was assigned to their own personal nutrition coach in order to receive not only guidance and/or answers to diet-related questions throughout the dieting period, but some extra support as well.
Training was comprised of a 4-day, upper-lower resistance training split. Each session was supervised by research assistants and sets were made sure to be completed at about 1 repetition from failure. Sets and repetition ranges varied over the 7 weeks, going from 3 working sets and progressing towards four sets of 6-8 and 8-10 (similarly for both upper and lower body days). Lastly, each subject was instructed to complete 30 minutes of low-moderate intensity cardio, twice per week.
The primary result of this study showed that the employing 2-day consecutive refeeds helps to preserve fat-free body mass during a fat loss phase compared to a continuous dieting protocol. This is an interesting finding, as the population being investigated are individuals who seek to maintain their lean body mass and ultimately improve their physiques.
A loss of bodyweight will not just come from fat stores alone, so implementing strategies aimed at maintaining our muscle mass is key in pursuing any successful and effective fat loss phase. With that said, having tools that can give us even the slightest bit of an edge is most likely worth using – this especially goes for those who are either experienced trainees/athletes, those who have established their nutrition and training routines, or a combination of the two.
Another finding, albeit a less significant one, was that resting metabolic rates (RMR) of the 2-day refeed group was maintained a little better than those of the continuous dieting group. This would indicate that an attenuation of metabolic adaptations was occurring here, although this result can also be tied to the fact that a preservation of fat-free mass was observed in this group as well (making RMR maintenance more of a secondary outcome). Overall both diet groups did well with adhering to their prescribed intakes and their training over the 7-week period and there were also no differences between the groups for training volume.
For resistance-trained, lean individuals looking to lose body fat, 3 key recommendations from the present study are to go about the diet with a high protein intake, a slow rate of weight loss, and employ intermittent “breaks,” or structured refeeds, within the dieting period.
These recommendations not only put us in a better spot to preserve muscle mass and get the most out of the time spent dieting but having refeed days can also prove helpful with overall compliance and flexibility for the dieter. Like diet breaks, refeed days can serve as something to look forward to in the week and placing them strategically (for example, parties and events) can help clients remain flexible within the diet while staying on track.
One more consideration to make is when the dieter may need a refeed. This while there is support for them, this doesn’t necessarily mean they need to be employed immediately upon entering a fat loss phase. From what we’ve seen with clients, longer and more aggressive diets (like contest preparation) can benefit from a refeed or two being thrown in down the line and/or as needed in order to help mitigate adaptations in those more extensive dieting bouts.
Campbell, B.I, Aguilar, D., Colenso-Semple, L.M., et al. Intermittent energy restriction attenuates the loss of fat free mass in resistance trained individuals. A randomized controlled trial. J. Funct. Morphol. Kinesiol. 2020, 5, 19.