The Truth About Refeed Myth – Part 1: Refeed increases the satiety hormone leptin

Refeed

a widely used method in the fitness industry that gives you the justification to eat more than you should on a weight loss diet. The idea behind refeed days is that higher calorie intake days improve your weight loss, increase satiety hormones and to boost your metabolism on a weight loss diet.

 

Refeeds are very popular among dieters. This isn't surprising because refeeds allow you to eat more calories – mostly coming from carbs - on one or two days a week. On refeed days calories are usually increased up to the individual energy maintenance requirements or are set even higher to create a slight surplus. Your weight loss is supposed to benefit from it, because refeeds are thought to:

  • Improve fat loss
  • Boost metabolism
  • Increase the level of the satiety hormone leptin, which drops shortly after going on a weight loss diet
  • Reduce hunger
  • Improve diet adherence
 

The refeed concept is pretty neat, particularly for a semi-starved dieter who is obsessed with food he/she can’t eat on a weight loss diet. Don’t we always want the things we can’t get? 

The best thing about a refeed day is that you don’t need to feel guilty eating the food you shouldn’t eat on a weight loss diet because a refeed gives you the ideal excuse to do it. Refeeds are supposed to be good for your diet!

Yet, I am very sceptical about things that sound too good to be true. This also applies to the refeed concept. For this reason, I decided to put numbers taken from the research literature on the supposed benefits of a refeed. This way, I will provide you clear and transparent information on how beneficial refeeds truly are, so that you can decide whether they benefit your diet or are a setback for your weight loss goal.

 

Refeed's influence on the satiety hormone leptin

The main argument why dieters should refeed is that short-term increased carbohydrate intake boosts the satiety hormone level. This hormone – leptin, to be more precise - drops shortly after the start of a diet.

Here, the important key word: SHORTLY

Already 6 hours after a meal the leptin level start dropping.

Thus, the question that instantly comes into my mind is:

Why should I waste a day of dieting by not losing any weight or maybe even gaining some weight, in order to increase my leptin level, if it already drops on the next day (after I fasted overnight)?

To put a few numbers on it to make it clearer:

-         40% energy surplus created by overeating on carbohydrates for 3 days increases leptin level by about 27%

-         Eating as little as 140 kcal by 1 pm after an overnight fast makes leptin level drop by about the same percentage as 40% overeating on carbs for 3 days increases it

 

 Influence of energy intake on leptin level. Three days overeating lead to 27% increase in leptin. Dieting until 1 pm leads to 27% decrease in leptin.

Influence of energy intake on leptin level. Three days overeating lead to 27% increase in leptin. Dieting until 1 pm leads to 27% decrease in leptin.

 

The findings above don’t sound like a very convincing argument in support of the refeed concept. As the leptin level respond to changes in nutrient intake so quickly, it is unlikely that the effect of one day refeed will be maintained until the next day.

 

There is another interesting study in support of the point I made above. This study compared the effect of skipping breakfast vs eating a carbohydrate-rich breakfast on leptin levels. Both groups - breakfast-skippers and breakfast-eaters - were provided with a carbohydrate-rich lunch they could eat as much of as they wanted. It is not surprising that the breakfast-skippers ate more food for lunch compared to breakfast-eaters. However, a fact that may appear somewhat surprising is that breakfast-skippers had significantly lower leptin levels in the afternoon despite eating more carbs for lunch. Indeed, their leptin levels were as low as during their morning fast. Thus, it seems like one carbohydrate-rich meal is not enough to compensate for fasting in the morning.

Another surprising fact is that even though breakfast-skippers had a significantly lower leptin levels than breakfast-eaters, their appetite scores didn’t differ. This mean that having less leptin in your blood stream doesn’t make you hungrier, at least short term

 

This finding is supported by another study, in which the subjects were put on a 62% energy deficit diet for 2 days. After 2 days of this severe calorie-restriction they were allowed to eat as much as they wanted for another 2 days. The energy restriction lead to a 27% drop in leptin. No wonder that the participants overate after the calorie-restriction was over. However, there was no association between the decrease in leptin at the end of the diet and the degree of overeating the days after. This finding shows once again that a lower leptin level doesn’t make you more hungry. 

 

Up to now I described short-term leptin changes, but does the same apply for long term dieting? A person who wants to lose weight doesn't diet for one or two days after all. It often takes weeks or even months to reach the desired weight loss goal.

 

The first and most important point to mention is that leptin is not only dependent on the current energy intake and nutrient status, but also on the body fat percentage. The more body fat a person has, the higher is this person’s leptin level. Leptin levels can differ by over 7-fold for individuals with different body fat percentages.

 Body weight has an influence on leptin. Individuals with a higher body weight produce more leptin.

Body weight has an influence on leptin. Individuals with a higher body weight produce more leptin.

 

For this reason, it is not surprising that leptin level drops when a person loses a significant amount of fat. Trying to maintain the leptin level at the pre-dieting value is like losing lots of weight while hoping that the clothing size won’t change, because one doesn’t want to buy new clothes. No matter if you want it or not, weight loss results in a smaller clothing size and a lower leptin level. That’s how the nature works.

Thus, the question is: Why the hell should we try to maintain initial leptin level while dieting if it will drop anyway?

 

Even refeed-friendly dieting protocols, such as alternate day fasting, lead to a 40% leptin drop over 12 weeks dieting while the dieters lost about 5.2 kg. This dieting method alternated one dieting day with an energy deficit of 75% with one refeed day during which the dieters could eat as much as they wanted. It’s like having a refeed every other day. Yet, the leptin level dropped despite refeeding half of the dieting time.

In another 12-week study that used a more realistic dieting protocol with a daily deficit of about 680 kcal (480 kcal deficit from reduced food intake and 190 kcal deficit created by exercise) leptin levels decreased by 54% already after the first week of dieting. Leptin remained low until the end of the diet without being significantly different from the value measured after the first diet week. 

This means that after an initial drastic drop, leptin level doesn’t change much until the end of the diet (at least if one diets for a few months). The decrease in leptin level was not associated with the amount of weight or fat lost. However, leptin decrease was associated with the feeling of hunger and the desire to eat.

In contrast to the findings I described above that an acute leptin drop doesn’t make one hungrier, this may not apply for long term dieting. If you diet for several weeks, a higher drop in leptin may make you hungrier.

Yet, even if it is the case, this information doesn’t help us when it comes to real-life application. It seems like we can’t do anything against a leptin drop that occurs when we reduce energy and carbohydrate consumption on a weight loss diet.

Refeeds may increase leptin for less than 24 hours, but most likely not for longer. For this reason, there is just one thing you can do:

Suck it up and don't try to be smarter than the nature by attempting to manipulate your leptin level.

 

 Short-term increased carbohydrate and energy intake may increase leptin short-term, however, this doesn't transfer to increased fat loss. If you aren't in energy deficit, you don't lose fat. 

Short-term increased carbohydrate and energy intake may increase leptin short-term, however, this doesn't transfer to increased fat loss. If you aren't in energy deficit, you don't lose fat. 

 

But what about refeed's metabolism boosting effect? Does a refeed day increase my metabolism and make me burn more fat?

Metabolism boosting effect will be the topic the next part of the ‘The Truth About Refeed Myth’ series. Stay tuned!


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