In my last article I answered the question ‘what is metabolism?‘. In that article I explained that metabolism (the number of calories you burn in a day) is essentially the sum of three parts:
- Your Basal Metabolic Rate (BMR) (the number of calories you burn performing the basic functions that keep you alive).
- Your level of Physical Activity.
- The Thermic Effect of Foods that you Eat (the number of calories it takes to digest and absorb the foods you eat).
In the past I have written about the effect food has on your metabolism. However, after reviewing these articles I have discovered that some of the information in them is not 100% correct. That’s why today I want to revisit the topic of food and metabolism to explain exactly how eating can affect your metabolism.
WHICH FOODS CAN BOOST YOUR METABOLISM?
As you can see from the list at the start of this article the main way food affects your metabolism is through its thermic effect. The thermic effect of foods is relatively static. However, there are certain foods that can give your metabolism a slight boost and I have outlined these below:
1) FIBRE:- Simple carbohydrates such as sugars, white bread and white pasta are much easier to digest than more complex, fibrous carbohydrates such as fruits, vegetables and whole grain products. On top of this high fibre carbohydrates have a number of fantastic health benefits and fruits and vegetables are a rich source of vitamins. Therefore, by making the switch over to whole grain bread, pasta, rice etc, substituting some of your processed snacks (chocolate, crisps, etc) for fruits or vegetables and making fruit and vegetables a richer part of your main meals you can improve your overall health and give your metabolism a slight boost.
Why not try having a bowl of oatmeal with fruit for breakfast, a piece of fruit as a mid-morning snack, a whole grain sandwich or two for lunch, a handful of dried fruit for an afternoon snack and a vegetable rich evening meal? Not only will this be a much healthier choice and probably contain less calories than a diet which contains crisps and chocolate as snacks but it will also burn a few more calories during digestion and absorption.
2) PROTEIN:- Your body uses more energy when breaking down protein than it does when breaking down carbohydrates and fats. This was demonstrated in a study by McArdle et. al (1986)  which concluded that if you eat a meal consisting of pure protein up to 25% of the calories will be burned during digestion and absorption.
Most people’s diets today are rich in carbohydrates so increasing the amount of protein you consume and cutting down on the carbohydrates is another good way to provide your metabolism with a little boost. However, you need to make sure that you do not go overboard on the protein. Whilst extra protein can be beneficial eating too much places stress on a number of your vital organs including your kidneys. On top of this if you cut down on the complex carbohydrates or fats too drastically you will be missing out on a number of essential vitamins, minerals and fatty acids which can lead to a number of health problems. Vitamin deficiencies can also stop your body from performing certain functions and lead to you burning less calories.
3) SPICY FOODS:- Spicy foods give you a temporary boost in metabolism in two ways. First, certain spices have thermogenic properties i.e. they stimulate your body’s fat burning process. Cayenne, a red hot chilli pepper, is used as an ingredient in many diet pills for this very reason. Secondly, eating spicy foods raises your body’s temperature temporarily meaning that you will burn more calories as your body attempts to regulate this temperature increase.
Like with protein, eating a little more spicy food is another effective way to increase your metabolism slightly. However, spicy foods also need to be added to your diet in moderation. Eating too much can lead to stomach ulcers, an irritable bowel, heartburn, damaged taste buds and sleep problems.
4) WATER:- Drinking water does not boost your metabolism. However, it prevents you from becoming dehydrated. If you become dehydrated your body stops performing certain basic functions and therefore burns less calories. Therefore, whilst drinking lots of water does not exactly boost your metabolism it does prevents it slowing down.
WHICH FOODS CAN SLOW DOWN YOUR METABOLISM?
As I said above the thermic effect of foods is relatively constant. However, just as there are foods that can slightly increase your metabolism there are also foods that can slow it down. I have listed a number of these below:
1) ALCOHOL:- Alcohol itself does not slow down metabolism. However, it can lead to dehydration which affects your BMR and reduces the amount of calories your burn on a daily basis. On top of this many alcoholic beverages contain simple carbohydrates and sugars which require less calories to break down than more complex carbohydrates. Therefore, excessive alcohol consumption is likely to lead to a slight slow down in metabolism.
2) CAFFEINE:- Like alcohol, caffeine does not slow metabolism down itself. However, when consumed excessively it can cause dehydration which means that you burn less calories on a daily basis.
3) SIMPLE CARBOHYDRATES:- Simple carbohydrates such as white pasta, white bread and sugary foods require slightly less calories to digest and absorb than more complex, fibrous carbohydrates.
DOES MEAL FREQUENCY AFFECT YOUR METABOLISM?
In a number of my previous articles I highlighted the importance of eating mini meals to boost your metabolism. However, after reading up on the subject I found that this may not be the case and I may be wrong when it comes to the impact mini meals have on your metabolism. This post from Fitness Spotlight sums it up quite well but the general logic is that the amount you eat affects how many calories you burn through digestion and absorption. Logically it makes sense. Let’s say for example a chicken breast takes 100 calories to digest. It’s still going to take 100 calories to digest whether you eat it all at once or as part of two mini meals. Although I have said in the past that mini meals are essential for boosting your metabolism I have to admit that this was an area where I was wrong. Despite the popular rumour, meal frequency does not affect your metabolism unless the total amount of calories changes. Skipping meals will not slow down your metabolism. Eating more meals will not increase your metabolism.
However, just because the frequency with which you eat food does not affect your metabolism this does not mean mini meals are useless. As Mike (from the IF Life) says eating more frequently can help you lose weight because people are generally advised to eat complex carbohydrates and protein as part of their mini meals. These nutrients help keep you fuller for longer and are generally lower in calories. Mini meals also help reduce cravings and stop you feeling hungry meaning that you are less likely to over eat and binge on calories.
I hope this article has shown you that the food you eat does NOT have a massive impact on your metabolism. By making sure your diet is rich in fruits, vegetables and protein (without containing excessive levels), keeping yourself hydrated and perhaps eating a few more spicy meals you can give your metabolism a small kick. However, the thermic effect of food only accounts for 10% of the total calories you burn in a day so the type of food you eat is never going to have a massive impact on your metabolism. The frequency with which you eat these foods also does not have an impact. The key factor is how much food you eat and how many calories you consume. Yes eating more fibre, protein and eating smaller meals more regularly may help you lose weight BUT this is because you are eating less calories and because you feel less hungry NOT because your metabolism has significantly increased.
What do you guys think? Do you agree that the type of food does not have the massive effect on metabolism that some people think? Do you think the total amount of calories consumed is the deciding factor? Let me know your thoughts by leaving a comment.
 McArdle, W.D., Katch, F.I., Katch, V.L., (1986) Exercise Physiology: Energy, Nutrition, and Human Performance Lea and Febiger Philadelphia p. 134, 135
Eating More Meals Does NOT Speed Up Your Metabolism (Fitness Spotlight)