The truth about metabolism

Does eating breakfast really kick-start your metabolism?

What about exercising in the morning?


The truth about Metabolism

Metabolism – –  The technical definition…
“The chemical processes that occur within a living organism in order to maintain life”

However, when used to describe or explain weight loss, most people think of it as the following…

The amount of fuel / calories we burn each day.

MOST of the fuel we burn each day is used just to keep us alive…
To keep our heart beating, our brain functioning and our cells regenerating.  Even if we don’t move a muscle. This is known as our BMR – – Basal Metabolic Rate.

**Imagine a car burning fuel with its engine running but parked in the driveway all day long.

I discuss how many calories you burn each day HERE, including a calorie calculator and a video lesson. How many calories do I burn each day?

The harder our body works, the more fuel we use..


  • resting burns 1 cal per minute
  • moving burns up to 4 cals per minute (body working harder)
  • exercising hard burns up to 10 cals per minute (body working even harder)

Some other examples of how our body “works harder”

(hence more calorie burn / higher metabolism)

  • body temperature regulation (either cooling us down or warming us up)  = working slightly harder = very small increase in metabolism
  • the process of eating / digesting food =  working harder = increased metabolism (don’t get too excited, its only a small percentage of the calories we eat)

Let’s go back to our car in the driveway with the engine running (resting) example.

Obviously the car “works harder”,  when it drives around. It burns more fuel (increases metabolism).

However this is a temporary action, once the car returns back to the driveway (resting), the amount of fuel burn (metabolism) returns to the lower rate. The same is true when talking about our increased metabolism. It is usually a temporary action. The metabolism resumes back to normal level when the action that increased it is complete.


Lets investigate the following common statements…

“Eating breakfast increases our metabolism” .

Yes, as already stated,

Eating / digesting = body working harder than resting = slightly increased fuel burn (increased metabolism).

However the metabolism returns back to normal once the digestion process is finished. It does not matter what time of day the eating occurs.

Therefore the statement “eating breakfast increases our metabolism” is technically true. (any eating / digesting  increases it slightly)

However this statement “eating breakfast kick-starts our metabolism for the rest of the day” is not true. The metabolic rate resumes to normal level once the digestion process is complete.

***Links to scientific studies can be found at the bottom of this blog post.

Next statement to investigate..

“Exercising increases our metabolism”

Yes of course.

Exercising = body working harder = more calorie burn (increased metabolism).

However, just like the breakfast eating example, the metabolism returns back to normal when the body is finished and recovered from the exercise session. You can read HERE about how certain exercises prolong the increased metabolism effect.

In summary (and some extra info)

  • Our metabolism is running all of the time, not just when we exercise (if it wasn’t we would be dead). This means of course that we are burning calories all of the time.


  • We burn more calories when are moving compared with when we are resting. (A car burns more fuel when it is driving around than sitting in the driveway with the engine running)


  • We burn even more calories when we exercise (like when the car is accelerating or going up a hill)


  • Our metabolism raises slightly when we eat something because it takes energy to digest the food. Certain foods take more energy to digest than others. Protein and fibrous veg can use up to 30%  of their calories in the digestion process alone. Processed carbohydrates use hardly any energy at all. I have written in full about it HERE


  • Contrary to popular belief, a larger person usually has a higher metabolism than a smaller person (a larger car burns more fuel than a smaller car)


  • A person with more muscle on their body has a higher metabolism than a person of a similar size but with less muscle (take 2 similar size cars, but one has a V8 engine hidden under the hood)


  • When we talk about increasing ones metabolism, we usually mean for a limited time. Example – “Eating XX food increases your metabolism”.  Yes this might be true, but it is just for a small period of time until that food is digested, then the metabolism resumes back to normal levels.


  • We can slow down the metabolism by consuming  inadequate, quality nutrients over a prolonged period of time (sorry I don’t have a car analogy for this one). Again, this is usually true for a short period of time or until we increase the amount of nutrients we put in. The metabolism should then return to normal levels.


  • The metabolism might slow down long term if the lack of nutrients also caused us to lose some muscle mass.  (This happens after  a lot of fad diets, particularly shakes, juice cleanses and low protein diets)


  • We can increase our metabolism by increasing the amount of muscle we have and ensuring we get enough nutrients in our meal plan. (Notice I talk about adequate NUTRIENTS, not just calories. It is possible to eat a LOT of calories, but still not get enough essential nutrients (if your diet is crappy). It is also possible to eat fairly low calories (not lower than 1200 per day), but get a LOT of nutrients if you choose well. I have written about that HERE (pics included)


  • A VERY small percentage of people have an unusually high metabolism and can eat more than most people, yet not put on weight. However MOST (almost all) of the time, its because that person is moving more (not necessarily exercising) and / or eating less calories (not necessarily less food). See how that works HERE .  ** Medical issues aside.


  • Yes its true that our metabolism slightly slows down as we age. This can be due to…
  • A) loss of muscle mass. This can be prevented by regular resistance training and consuming adequate protein.
  • Please also see Are you losing muscle?
  • B) sometimes we simply move less as we age, this is not directly BECAUSE we age. This can be rectified by getting a minimum of 10,000 steps per day
  • C) a change in hormones.

Personal note on eating breakfast

I LOVE my breakfast.

I wake up hungry… really hungry. Breakfast is my favourite meal of the day. However, I know that not everyone has the same hunger patterns as me. I believe in eating when hungry and stopping when satisfied. If you are truly not hungry in the morning, then don’t stress about waiting a little later til you eat. Your metabolism will be just fine. The fine line is to eat when “fairly hungry” and not to wait too long til you are ravenous.

The TOTAL number is what's important
The TOTAL number is what’s important

Scientific studies on eating and metabolism

Please  view this study from Bath University, which states..

“The common conception that breakfast may facilitate weight management by ‘kick-starting metabolism’ was not evident at all in our results, with resting metabolic rate stable within just 11 kilocalories per day from the start to the end of the intervention in both groups.”

Or you could check out this study, or  this study from The American Journal of Clinical Nutrition

Or this study from the British Journal of nutrition, on meal frequency where participants were given the same calorie amounts split over 2 meals or 7 meals per day with no significant difference between the 2 groups.

Its the daily total that counts, not the timing.

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Chriss TinslayWould you like more help and coaching with your health and fitness goals?

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I believes that fitness and fat loss should fit into your fabulous life, NOT take over it.   You can connect with me on Facebook where she shares useful tips each and every day.