Intermittent fasting and the metabolism myth

Learn why intermittent fasting won't slow down your metabolism, but will actually help you burn fat! Eating five small meals a day is probably the most popular metabolism myth around. Find out what mountains of research have actually found about metabolic rate. I spent many years consuming misguided, unresearched information about weight loss and health. From women’s magazine articles to television segments to popular YouTube videos, I learnt many tips and tricks on how to boost metabolism. Or so I thought. 
 
Some were easier to implement, like drinking weight loss tea or eating more protein. While others were a little more difficult, like eating frequent small meals throughout the day. This myth is probably the most widely-believed and circulated weight loss rule of all time. Ask anyone what the best way to boost metabolism is and they will more often than not suggest eating five+ small meals a day. And for some people, this works. 
 
Although if you’re trying to lose weight, you’re probably cutting calories. I’ve seen weight loss plans suggest dieters should divide a measly 1200 calories into six small meals a day. Is it just me, or is there something that’s not all that satisfying about eating a 200 calorie meal? It’s also far too easy to go over this strict amount and eat more. 
 
All these practices are in the hope of achieving a faster metabolic rate. The idea is that way you’ll burn more energy throughout the day and lose weight. It makes sense on paper. But is there any science to back up the claim that eating frequently increases metabolic rate?
 
This article covers:
  • What actually is a metabolism
  • What determines metabolic rate
  • Science-backed facts about eating frequency and metabolism
  • Insulin and its impact on weight loss
  • Why breakfast isn’t the most important meal
  • The fat-burning benefits of intermittent fasting 
Find out what science says about eating frequently, boosting metabolism and intermittent fasting. 
 

What is metabolism?

The word metabolism describes the chemical reactions that occur within the body to survive. These include processes like growth and energy production. When the term is used in the media and conversations, people are usually actually referring to metabolic rate, which is the rate at which the body uses energy, or burns calories. Attempts to influence and increase metabolic rate have gained popularity in the weight loss industry over time. The logic is that a faster metabolic rate will cause greater calorie burn throughout the day and lead to weight loss. This can be an effective strategy for long term weight maintenance. But unfortunately, due to the many widely circulating myths about metabolism, many people use techniques that simply aren’t back by science. The term “boosts metabolism” has basically become and overused marketing slogan. 

What determines metabolic rate?

This is probably one of the most misunderstood bodily functions. The metabolic rate refers to how much energy your body uses to run. There are two popular but contrasting opinions about metabolic rate:
“I was born with a slow metabolism so I’ll always be overweight,”
 
or: 
 
“I’m going to try every single technique to speed this bad boy up.”
 
Personally, I’ve bought into both. But I found it easiest to actually lose fat when I took my focus off metabolism!
 
The body burns energy (kilojoules or calories) in a few ways:
  • through the energy required to keep functioning while at rest. This is known as the basal or resting metabolic rate (BMR or RMR) 
  • through movement as part of everyday activities 
  • through deliberate exercise. 
But the rate at which the body burns energy is dependent on a few factors. Genetics can play a huge role. That’s why some people can (unfairly) eat whatever they want and stay slim, while some seem to pop a button just thinking about a slice of cake. But luckily, there is a surefire way to increase energy burn… 
 
Exercise is one of the most effective ways to increase metabolic rate. Simply, if you think about the body as a car, it uses less fuel (energy) while idling in a drive way. It’s the same with the body when sleeping or sitting. But when you put the pedal to the metal and accelerate, you consume more fuel to move. When you exercise, the body needs to use more energy to fuel your muscles to achieve a similar movement. 
 
However, most efforts that claim to boost metabolism are usually focused on increasing the basal metabolic rate – how much energy you body burns while resting. From the example above, it’s easy to see why putting slices of lemon in your water bottle and eating every three hours will not directly give you the ab definition you may crave. 

So why are we told to eat five+ times a day?

This metabolism myth has to be by far the most believed but unfounded concept in the health sector. There are a number of reasons this idea works on paper. 

The theory of eating frequently

 
Many people assume the metabolism is similar to a fire – the more often you stoke it, the more ferociously it will burn energy throughout the day. There are a few other contributing factors: 
 
The calories it takes the body to digest food, known as the thermic effect of food, is also believed to increase with eating frequency. Logically, it makes sense that the more often you eat, the higher this burn rate will be. 
 
Eating more frequently can also help some people control their appetite and stop them from overeating at main meals. But that doesn’t make it the perfect eating pattern for everyone. In fact, it’s very easy to overeat. 
 

But science says otherwise…

The “eating 5+ small meals a day” theory has ZERO research to back it up. 
 
This recent study found there is was no noticeable effect on fat loss from eating breakfast versus skipping it in overweight adults trying to lose weight. While this study of a group of obese women on a 1000cal/day meal plan found no difference in energy metabolism between the women who ate 5 times per day and the women who ate twice. Just to top it off, this review of 10 weight-loss interventions found there was no association between eating frequency and weight or health.
 
Some dieters also fear the if they don’t eat frequently, their body may mistake their skipped breakfast as a complete lack of food. In this case, the body may enter starvation mode and slow metabolic rate to compensate. 
 
While the metabolism can slow in times of famine, research suggests it actually takes the body about three days to do this. However, you’re much more likely to experience this slow in metabolic rate from weight loss or long term calorie restriction.
The “eating 5+ small meals a day” theory has ZERO research to back it up. 

Insulin

For a brief biology lesson, pretty much every cell in the body relies on glucose to function which they get from food. It’s therefore very important for the body to keep blood glucose (sugar) within certain limits. The body does this with two hormones: insulin and glucagon. 
 
When food is eaten, the level of glucose in the blood rises. High blood glucose levels cause the pancreas to release insulin. Insulin stimulates the uptake of glucose by cells causing levels in the blood to decrease. This outline is part of the insulin feedback loop that keeps you alive. 
 
Insulin is a storage hormone. It tells your body to store the goodness that’s floating around your body – including fat (simply put). It’s production is stimulated every time you eat. 
 
Frequently eating means the body is constantly producing insulin. Chronically elevated insulin levels isn’t too good for the body. Not only can it make fat loss more difficult, but it can lead to a few nasty conditions including insulin resistance and type 2 diabetes. 
 
For some people, this isn’t really an issue. But for the many people that are predisposed to insulin resistance and type 2 diabetes, eating frequently and constantly spiking insulin levels may not be the healthiest option. 

Breakfast isn’t the most important meal of the day

We’re often told that breakfast is the most important meal of the day. However, most popular breakfast foods contain refined carbohydrates, little protein and barely any healthy fats. Yes, some research suggests people who eat breakfast tend to have a lower BMI. However, correlation is not causation. 
 
But eating breakfast doesn’t “kick-start” your metabolic rate like many so-called health gurus say it does. Instead, recent research has found eating breakfast compared to skipping doesn’t appear to impact body weight at all. While this trial divided a group of overweight adults seeking to lose weight into breakfast eaters and breakfast skippers. It found breakfast habits had no discernable effect on weight loss.
 
If you’ve eaten breakfast every morning for most of your life, it’s natural that you get hungry at this time – it is not a sign of your body entering starvation mode or your metabolism slowing. 
 
In fact, skipping breakfast has become a popular weight loss and fat burning technique known as… 

Intermittent Fasting

When the false idea of eating frequently to increase metabolic rate became popular, fasting quickly fell out of fashion. Many people feared not eating would immediately slow down their metabolism. 
 
Above, we saw how the body deals with elevated blood glucose levels. But quite the opposite happens when the body is in a fasted state and blood glucose begins to drop. This triggers the release of the catabolic hormone, glucagon. Unlike insulin, glucagon tells cells to release and burn energy rather than store it. 
Once the body has used up its glycogen stores, it starts to burn fat. 
Fasting causes this process to happen. Once the body has used up its glycogen stores, it starts to burn fat. That’s why we have fat in the first place – to burn in times of need. But unfortunately, modern lifestyles have meant that we rarely fast or burn fat. So the body just keeps accumulating it for later. 
 
It’s important to note that this fat burn process doesn’t happen nearly as effectively when insulin levels are constantly spiked from eating frequently. That’s why intermittent fasting is such an effective fat burning tool for most people. 
 
Find out more in the article, The Beginner’s Guide to Intermittent Fasting

Conclusion

  • Most people are actually talking about metabolic rate when they say “metabolism.”
  • Contrary to popular belief, breakfast is NOT the most important meal of the day. 
  • There’s no metabolic advantage from eating frequently. You don’t have to eat 5+ small meals a day.
  • In fact, periods of fasting can be beneficial to the body and for weight loss, and it WILL NOT slow your metabolic rate.
  • An easy way to slow your metabolism? Weight loss
  • The most effective way to boost metabolism? Exercise!

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