Refeed Days—How Effective Are They, Really?

By Body Coach Holger Gugg

Dear blog readers,

Today I’m addressing “refeeding,” a topic that couldn’t be more popular or hyped.

Many people still view “refeeding” as a term for intentional deviations from their diet plan. As a result, “refeed days” are often specifically scheduled during periods of isocaloric or hypercaloric eating—which, at least from a metabolic and physiological perspective, is absolute NONSENSE. Anyone who uses refeeds while in a well-nourished state does so because they need it for their mental well-being. Or, to put it bluntly, because they’re weak and can’t resist. Under no circumstances should any positive effects on the distribution of fat mass or muscle mass be expected. Let’s get this out of the way right from the start, without any unnecessary beating around the bush. The question we’re addressing today is how a refeed day affects the body during prolonged hypocaloric phases and what effects one can actually expect.
Enjoy the read!

Refeed Days

In the fitness community, a refeed day is defined as a 24-hour break from one’s usual diet plan, used specifically to consume large amounts of carbohydrates. Some people keep their protein and fat intake constant during this time—which, of course, results in a larger calorie surplus—while others deliberately minimize their fat intake. They do this, on the one hand, to prevent increased fat storage in fat cells and, on the other hand, to keep the calorie surplus—which often occurs on these days—within limits. Refeed days are typically scheduled once a week. They differ from so-called “cheat days” in that they are “planned” and strategically structured, whereas a cheat day means a day without any guidelines or rules. Typically, people consume particularly high-calorie fat-carbohydrate combinations with a relatively low protein content on these days.
According to the principles of refeeding, the longer a weight-loss phase lasts and the greater the calorie deficit, the more important a refeed day becomes. In particular, this addresses a lack of carbohydrate intake.

Conclusion
: The classic refeed day takes place once a week as part of weight-loss diets. There are no set guidelines on exactly when to schedule it or how it should be structured (how many calories, which foods, etc.). However, the fitness press repeatedly advocates for the targeted consumption of large amounts of carbohydrates on these days to “get the metabolism going again.”

Leptin—That’s What It’s All About!

To understand the underlying rationale behind refeed days, you need to be fundamentally aware of one thing. Our bodies cannot distinguish between intentional food scarcity (dieting) and genuine food scarcity caused by a lack of available food. If a food shortage persists over a longer period, our body strives to hold on to its evolutionary energy reserves—namely, body fat. To do this, it employs several extremely effective tools, of which leptin is arguably one of the most powerful.

In my three-part series on “Regulation of Hunger and Satiety,” I present leptin as part of the so-called orexic network and thus as arguably the strongest “anorexigenic” (hunger-suppressing) signaling molecule, which interacts with and has a lasting influence on numerous other components of this complex. It can be said that whoever understands how to manipulate leptin understands how to influence long-term satiety. In fact, in addition to regulating the onset of satiety, leptin also controls systems such as skeletal muscle, adipose tissue, the liver, and the pancreas, promoting increased lipolysis and fat oxidation while suppressing lipogenesis and insulin production.

In addition to genetics, diurnal fluctuations in the circadian rhythm, sleep patterns, and physical activity, the prevailing body fat content (from which leptin is produced and released into the blood) (1)) and caloric intake also influence leptin levels. Since there is a close relationship between insulin and leptin, it is indeed possible to identify a specific influence of carbohydrates within the caloric intake (1–4). Coleman et al. wrote the following in their 1999 study:
“There is convincing evidence that insulin increases leptin synthesis and secretion, probably through an insulin-dependent effect on glucose metabolism.”

The relevant outcomes of reduced leptin levels caused by the aforementioned factors are ultimately:

• increased hunger (5)
• a decrease in 24-hour energy expenditure (3)
• (associated with reduced thyroid hormone production)
• reduced lipolysis and fatty acid oxidation (3)
• increased secretion of insulin and cortisol (3)

Recent studies have focused specifically on the first component mentioned and report that there is a direct link between weight loss in kilograms and an increased sense of hunger. According to Polidori et al., the result of this development was an instinctive increase in caloric intake of 100 calories per kilogram of weight lost—a figure of significant importance, especially when it comes to maintaining the achieved weight even after the weight-loss program has ended (9).

Conclusion
: Leptin is one of the body’s most potent hunger-suppressing signaling molecules, which also has a lasting influence on other bodily functions. The notion that “refeeds require carbohydrates” can, at least in theory, be confirmed primarily due to the interaction between leptin and insulin.

Short Refeeds Are Sufficient

In Part 2 of my article “What Really Fills You Up” (3), I cite several studies, such as that by Kolaczynski et al. (6). The researchers found that a decrease in leptin levels was observed after just 12 hours of fasting, but they also demonstrated that baseline levels could be restored as early as 24 hours after resuming normal food intake. Weigle et al. (7) discuss a disproportionate decrease in leptin associated with the loss of body fat, but also mention a refeed lasting only 12 hours, which restored leptin levels to their baseline after fasting-induced declines. My article “Some Thoughts on Your Competition Diet – Part 2” (8) also addresses the topic of refeeding. For the first time, following all the evidence regarding the short-term influence of one-day refeeds on leptin levels, extended continuous refeed windows of 3 to even 5 days are discussed here—which, when properly structured, should result in virtually no increase in fat mass.

Conclusion
: Leptin levels can be influenced in the short term through a severe calorie deficit, but much more significantly through the loss of body fat (reduction). Numerous studies consider 24 hours to be a sufficient time window to normalize leptin levels again.

Metabolic effect uncertain

In fact, there is even more interesting research on leptin and refeeding. Rosenbaum et al. subjected male and female participants to a severe caloric deficit of only 800 kcal/day until their body weight had decreased by 10%. Before the intervention and after the weight loss had stabilized, the researchers measured TSH, T3, and T4 (thyroid markers), as well as resting energy expenditure (REE), non-resting energy expenditure (NREE), total energy expenditure over 24 hours (TEE), and the thermic effect of food (TEF). As expected, reductions were observed in T3, T4, NREE, and TEE, while REE and TEF remained unchanged. Subsequently, all participants received a relatively high dose of exogenous leptin (0.08 mg/kg fat mass and 0.14 mg/kg twice daily). A follow-up measurement after 5 weeks of administration showed that all markers (T3, T4, NREE, and TEE) had returned to their baseline levels prior to the intervention. The researchers noted that the administered dose of leptin was far higher than what would have been achievable through a single refeed day (10).
Other studies, such as that by Chin-Chance et al. (11), show that a 3-day refeed (130% above TDEE with 50% of calories from carbohydrates—here, approximately 485 g/day) triggers an increase of 0.6 ng/mL in blood leptin levels. For a 70-kg man with a blood volume of approximately 5.3 L, this would correspond to a total increase of 0.003 mg. This contrasts with the 1.68 mg that was injected in the study mentioned above.
Rosenbaum et al. (12) investigated the effect of three 3-day diet regimens on normal-weight women, each with a 40% caloric surplus above measured energy expenditure (TEE):

• ISO OF 55% carbohydrates, 35% fat, 15% protein
• CHO OF 64% carbohydrates, 25% fat, 11% protein
• FAT OF 35% carbohydrates, 55% fat, 11% protein

As it turned out, fat overfeeding (Fat OF) had no significant effect on leptin levels or total energy expenditure (TEE). Carbohydrate overfeeding (CHO-OF) caused a 28% increase in leptin levels and a 7% increase in total energy expenditure (TEE), which, in numerical terms, corresponds to a daily excess calorie expenditure of 126 kcal. Of these 126 kcal, 36 are attributable to changes resulting from the thermic effect of food (TEF), which are solely due to the increased carbohydrate intake. To produce this effect, the participants had to consume 670 additional calories per day, corresponding to a net result of +544 calories per day from this intervention.

Conclusion
: Studies demonstrate an effect—particularly from carbohydrate-rich refeeds—on leptin levels. Based on this, there is also an increase in total calorie expenditure, though it is comparatively small.

Are Refeeds a Waste of Time?

Although the purely metabolic and energetic yield of a refeed—even if it lasts 3 days—is rather low, there are still compelling reasons in favor of refeeds.
One of these has to do with glycogen resynthesis, that is, replenishing depleted glycogen stores, primarily in the muscles. If these stores are depleted during a weight-loss program, this results not only in a loss of muscle mass but also in reduced training performance. Ultimately, in conjunction with gluconeogenesis, this can contribute to a loss of muscle mass.
When large amounts of carbohydrates are consumed over a short period, this causes the liver—and especially the muscles—to store glucose in the form of glycogen. Friedmann et al. provide a very specific answer to the question of how quickly carbohydrate stores can be fully replenished. According to them, the process takes 24 hours, provided that between 500 g and 700 g of carbohydrates are consumed (13). The likelihood of regaining body fat during a planned refeed is very low. Acheson et al. (14) report in their study that there is a threshold of approximately 500 grams of carbohydrates that can be consumed after glycogen stores have been completely depleted without simultaneously triggering fat storage. More specifically, this means that only after the carbohydrate stores have been fully replenished will any additional carbohydrates consumed be oxidized to a greater extent, but they will also be utilized in de novo lipogenesis. The maximum yield here is about 150 g of body fat per day, which requires an additional 475 g of carbohydrates daily.
According to various sources, glycogen storage capacity ranges between 350 g and 600 g. A figure of 15 g per kilogram of body weight, based on a ratio of 1 (liver) to 3 (muscle), is also cited in the literature; however, this figure appears highly inaccurate, as it does not account for individual body composition. If you want to know the exact figure, you should follow the instructions in my book *HBN – Human Based Nutrition* to determine the precise amount of carbohydrates for your refeed.

Conclusion
: Refeeds can have a gentle effect on existing muscle mass without rebuilding body fat. For this plan to work, you need to know your individual glycogen capacity. For this purpose as well, limiting yourself to a single refeed day is sufficient.

Appetite Regulation

One aspect that, as described above, is increasingly becoming the focus of diet research is the appetite-stimulating effect of a reduction in body weight or body fat. Since leptin is considered one of the strongest factors influencing the regulation of hunger and satiety, the importance of “leptin-relativizing” refeeds is taking on a whole new significance. On the one hand, they can ensure that weight-loss phases are completed successfully and without slip-ups; on the other hand, they also guarantee that once a desired state is achieved, it can be maintained. In addition to this actually measurable effect (9), there is, of course, the psychological aspect of refeeds, which must not be overlooked. Looking forward to a “special” day serves as a major additional motivator alongside the sense of accomplishment. Anyone who has already completed a weight-loss phase can certainly attest to this.

Conclusion

Refeeds help raise leptin levels again. As leptin levels rise, those annoying feelings of hunger—which often turn weight-loss phases into an absolute ordeal and remain a problem even afterward—fade away.

Summary
At the end of the day, I can finally give the all-clear to all fans of the refeed day. What initially didn’t look promising from a metabolic standpoint is put into perspective by other compelling reasons that actually support incorporating regular refeeds. As for the question “How often?”, today’s post shows that there’s actually no reason to schedule more than one day for it. To the question “How?”, the answer is quite clear: “high in carbohydrates and tailored to your individual glycogen storage capacity.” Finally, there’s the question of “When to start?”—and there’s no definitive answer to this. The more weight you lose and the greater your calorie deficit becomes, the more your leptin levels will drop. The fewer carbohydrates you consume, the faster your muscles will become depleted of carbohydrates. Monitor your hunger and satiety levels, as well as your performance metrics during training, and use that to decide when it’s time to start refeeding.

Best regards
, Holger Gugg
www.body-coaches.de

Read also...

• Some Thoughts on Your Competition Diet – Part 1
• Some Thoughts on Your Competition Diet – Part 2
• Study: Getting Enough Sleep Leads to Better Results on Your Diet

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