Calorie counting - does it work?

Counting calories has been a mainstay of many weight loss programmes for a long time. However from a scientific point of view it would be an amazing coincidence if calorie counting did work. Why is this?

Calories in vs calories out?

When it comes to weight it is simple. We count the atoms that come in and then count the atoms that come out. OK, counting atoms is not a realistic proposition, but clearly it would be accurate. Unfortunately counting calories is not an accurate way of assessing potential weight changes as it misses out many of these atoms.

IN: When you eat food and drink you are actually taking in atoms of carbon-C, hydrogen-H, oxygen-O and nitrogen-N. A few traces of other elements are present, but the amounts of these are very small by comparison. You also take in atoms of oxygen-O when you breathe, for some reason nobody ever seems to take this part of the equation into account.

OUT: You can lose these atoms when you visit the loo. When you defaecate, the atoms you lose will have registered on the scales, but some will have never entered your body, but have been stored in the digestive tract. When you urinate you lose atoms that have been part of your insides. (Technically the tubes for your digestive tract and airways are outside of your body). You also lose atoms when you breathe out carbon dioxide-CO2 and water vapour-H2O. Carbon dioxide and water vapour make up 10% of the air you exhale and represent a possible route for atoms from carbohydrate, fat and protein foods to be released. Atoms of hydrogen-H and oxygen-O are also lost in the water-H2O that we lose as sweat. Shedding skin and hair are also other ways to lose atoms from the body. So to summarise:

Atoms coming in:-

  • Air - mainly O2 two atoms of oxygen in the oxygen molecules we breathe in.
  • Food and drink - CHO from carbohydrate, alcohol, water and fat. NCHO from proteins.

Atoms leaving our body:-

  • In the air - mainly CO2 and H2O. These make up 10% of the air we breathe out. In a day we typically breathe out 14,400 litres. That is equivalent to nearly 18kg of air and nearly 2kg of carbon, oxygen and hydrogen atoms.
  • In the urine - mainly H2O with some nitrogen-N and carbon-C, mostly in the form of urea. Urea makes up roughly 2.5% of urine and is half nitrogen. We typically lose 1-2kg in urine per day.
  • From the digestive tract - NCHO from undigested foods including the indigestible fibre components in food. At times NCHO¬†from sloughed off epithelial cells and bacteria lost from our digestive tract linings.
  • In sweat - H2O.
  • From skin and hair - NCHO from the proteins that make up our outer protective layer.

You are unlikely to find the above approach to weight management anywhere else, largely because nobody has developed it into a workable system. However, I have brought it to your attention so that you become aware that counting calories is not some absolute measure of our capacity to gain weight, but at best an approximation of how mass accumulates in our body.

Are all calories equal?

This is one of the most contentious questions in nutritional science. The answer is quite simply that not all calories are equal in terms of their potential effects on your body, including weight gain. Let's consider some ways in which calories are not equal to others:

  1. Some calories in food do not get digested properly and as a result are not absorbed into your body. A good example is resistant starch, which can sometimes be broken down in the colon into fatty acids, which either get absorbed, used by colonic bacteria, or get excreted.
  2. Different types of macronutrient, protein, fat and carbohydrate have different effects on our body, stimulating variable production of hormones such as insulin, amylin and leptin2. There are many studies that suggest that different macronutrients either have similar effects on weight gain or that they do not. I've not found one study that I find particularly convincing in this regard mainly due to small sample sizes and short periods of analysis. In other words a typical study includes only 10 people studied over the course of 24 hours. However common sense should prevail. The chance that your body will store the same amount of fat given the different types of hormone circulating in your blood is pretty slim. It will also differ widely between people.
  3. Most foods contain more than just protein, fat and carbohydrate. The effect of phytochemicals, including alkaloids and catechins found in coffee and green tea respectively are good examples. The alkaloid caffeine stimulates adrenaline and nor-adrenaline, potent agents of fat burning, while the catechin, EPG found in green tea affects levels of insulin, sex hormones and CCK, leading to less consumption and absorption of nutrients3.

Calorie counting in practice.

So calorie counting is at best an approximation, but does this mean that it is useless for controlling weight? This depends on the person who is trying to change their weight. There are a number of reasons why it can all go horribly wrong.

  1. A few people find it easy to follow a strict calorie controlled diet. However, most people don't. The problem is that controlling calories is either, a) a time consuming affair if you want to eat an interesting mixed, healthy diet or, b) boring and monotonous if you want to eat prepacked, unhealthy calorie-counted shakes or bars. These factors of effort and monotony mean that for most people staying with a calorie controlled diet long term does not work. This is backed up by the vast majority of dieters who have tried diets, often repeatedly, but still gain weight over the long term.
  2. Restricting calories can put the body under stress. This can cause hormones such as cortisol to circulate that cause fat to be deposited around the waist.1
  3. Wholesome nutritious foods are often missed out of calorie controlled diets as the emphasis is almost always on weight loss and not on overall health. Important vitamins, minerals and phytochemicals are often in short supply. These health giving nutrients are not always as readily available even if you add a high strength multi nutrient pill to your daily diet.
  4. The artificial sweeteners present in many calorie controlled diets can lead to symptoms such as headache and heart palpitations as well as increasing appetite and increasing cancer risk.
  5. The low fat products used in calorie controlled diets can lead to deficiencies in essential fats and fat soluble vitamins.

Whether you should completely ignore the amount that you consume is another matter entirely. Portion control can make a lot of sense if you are trying to change your diet and lose weight.

To summarise.

Calorie counting is all about the energy that can be liberated from food and liberated via exercise. However, it does not account directly for what gives the body mass - all its atoms! Calorie counting is a useful tool, but I get frustrated that almost everyone involved in the field of nutrition and dieting, use calories as an absolute measure that can be relied upon.

My take is that calorie counting is for a few special cases, often with support from a professional. It is not an approach to be taken on by yourself if you haven't considered all the possible long term outcomes. You will be best off changing your diet around to include no junk food and instead eat plenty of fresh meat, oily fish, seafood, nuts, fruit and especially vegetables.

Portion control and exercise are additional tools that are worth using if you have a specific weight loss goal. You need to review your weight change at the end of each week, and adjust portion sizes and exercise regimes to reflect the progress made.

References:

1) http://www.ncbi.nlm.nih.gov/pubmed/20368473

2) http://www.pnas.org/content/101/4/1045.long

3) http://www.jacn.org/content/26/4/389S.full