Calories in Vs. Calories out – Is it really that simple?

A topic that we all love… food. I’m sure we all know runners that are obsessed with what they put in their bodies, others not so much. It’s pretty common knowledge that the lighter you are, generally the easier it is to move quicker – in most cases and to a point of course. But is it as simple as cutting out the calories to lose that fat? Andy DuBois explains further…

Fat loss is easy, all you have to do is eat fewer calories than you burn or so many people would have you believe. If you aren’t losing weight then you are either eating too much or not exercising enough. Unfortunately the human body is a little bit more complicated than that and the calories in vs calories out model of fat loss has some serious flaws.

It's all about balance yeah?
It’s all about balance yeah?

1. Food isn’t just calories
One assumption calories in vs calories out makes is that the all the food we eat is converted into calories. This assumes that whether you consume fat , protein or carbohydrate (macro-nutrients) it is all going to be used for energy and no other purpose. This is an incorrect assumption.

Protein is used for muscle repair. It is also found in our hair , nails , skin and brain and it can be converted into a number of hormones essential for the body to function.

Fat is used for insulation , it is used in cell membranes , it makes up part of the fatty sheath that surrounds nerve fibres, it helps with the absorption of some vitamins and is a key ingredient in hormones and other chemical substances that are vital for the body to function.Carbohydrates are almost solely used for energy.

So depending on what you eat a certain amount of the macronutrients will be used for maintaining the cells in our body.A meal high in protein and fat will have a percentage of its potential calories used as building blocks for the body whereas a meal high in carbohydrates will be used solely for energy.

2. The numbers don’t add up.
According to the calories in vs out argument if I ate 100 fewer calories per day for a whole year I would lose 36500 calories or approx 4 kilos of fat. That sounds great you may think. What if I then kept this up for 10 years. I would then have lost a total of 40 kilos of fat. I currently weigh 67 kilos so I would then weigh 37 kilos!

Now 100 calories is approx 1 slice of bread . So I wouldn’t exactly be starving myself.

The good stuff
The good stuff

There have been a number of studies that have shown that people eating the same amount of excess calories put on vastly different amounts of weight. If the calories in vs calories out theory is correct then the amount of weight gain should be very predictable, instead it ranges enormously. Studies have also shown that it is possible to gain weight when eating fewer calories than your body supposedly needs to maintain weight.

3. It takes energy to store energy.
Energy is required to convert food into a form of energy that can be stored by the body. The amount of energy required depends on whether it is carbohydrate, protein and fat and which scientific paper you read! The macro nutrient composition of your meal will affect how many calories are burned in converting food into a storable energy source.

4. Different macro nutrients affect our bodies differently
Hormones such as insulin and glucagon affect our fat storage or fat usage systems. Other hormones like leptin and ghrelin affect our feeling of hunger and satiety and all of these hormones are influenced by what we eat. The primary influence is not the amount of calories that we eat but the type of food we eat.

If the calories in vs calories model out is correct then it shouldn’t matter if we obtain all of our calories from pure sugar or from lentils. If we eat fewer calories then we should lose fat. But sugar has a vastly different hormonal effect on the body than lentils.

5. Inaccuracies measuring calories
If the low-calorie theory is correct then it is important to figure out how many calories we need to eat and how many we are burning per day. After all 100 calories extra and you will put on 4 kilograms in a year! It is almost impossible to measure either the amount of calories you eat or the amount of calories you burn to anywhere near that degree of accuracy.

Any watch or machine that tells you how many calories you burn is making some pretty big assumptions. The amount of fat and muscle you have will affect your calorie usage, your genetics will also affect it, as will the amount of sleep you had, the temperature, the time of day, your stress levels and numerous other factors.

There are numerous calorie counters that will tell you how many calories are in a certain foods but the level of accuracy of these is very questionable. How many calories in an apple for example , a quick search on the net shows anything from 70-120 for the same size and type of apple.

If you are measuring everything you eat, and using a state of the art watch to measure your calories burned you are still only going to have an estimate that is maybe several hundred calories out. Clearly this isn’t a good way to go about losing fat.

The bad stuff
The bad stuff

6. All exercise is not the same
The more calories we burn during exercise the better. Right? Well what about exercise that doesn’t burn as many calories during exercise but raises your metabolism after your workout?

What about the hormonal response to exercise? Different exercise affects our hormones in different ways and our hormones affect fat storage , fat usage , muscle growth and numerous other bodily functions. High intensity cardio or weight training involving full body exercises will elicit a greater hormonal response than going for a walk. But if calories out is all that matters then whether we walk for 60

minutes or do weight training for 20 minutes as long as we burn the same amount of calories it shouldn’t make a difference. In the real world, weight training or high intensity interval training will have a far greater fat loss benefit than walking (comparing workouts burning the same amount of calories)

Why do some people lose weight when they count calories?
The primary reason some people are successful is that when people calorie count they choose healthier foods as they are often lower in calories. It isn’t the fewer calories that promotes the weight loss it’s the healthier food choices.

So if counting calories doesn’t work what should you do?
Whilst there is a raging argument going on between low carb, high carb, atkins, paleo, dukan, south beach or any of hundreds of other diets, I prefer to keep it simple. Eat a diet high in vegetables, a moderate amount of fruit, legumes, protein and good sources of fat, low in grains and cut out the processed stuff (it’s not really food).

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I'm a mediocre runner who can bat above his average when I train hard. A man of extremes, I do enjoy everything life offers and consider it an absolute pleasure just to be able to put one foot in front of the other and let my mind wander somewhere different.

8 thoughts on “Calories in Vs. Calories out – Is it really that simple?

  1. I have seen changes in my ability to train since minimising what I put in during exercise. I either wait till I’m finished or use just enough, I have less gut issues and don’t have lull periods now. It is all about eating the right energy source at the right time out of training for me making sure I have sufficient energy to train and recover. I don’t count calories but have an idea of what I can and can’t eat and adjust this to how I feel on any particular day.

  2. Great article by Andy. I agree fully with the described approach to daily eating too and am currently starting my own version of this. On the run Nutrition though is a different story for me, intensity of the run/race is the main dictator of my “on Run” energy consumption.

  3. I like to say JERF. Just Eat Real Food. If you adopt this approach then I think it’s about 95% correct. The battle between paleo, vegan etc is really over the last few percent. By not eating added sugar or processed food I find I can eat as much real food as I like and don’t put on weight. By eating more (good) fat and less sugar/refined carbs I have felt my energy level/fuel on long runs endure much longer; it even helps if I fast for a few hours before long runs. Thanks again for your great article; one extra point on why cals in/out doesn’t make sense is the observation that animals in the wild maintain relatively static weight despite their calorie intake frequently changing. John

  4. Totally agree with your article.
    One thing I just learned is that High-fructose corn syrup (HFCS) can only be processed by the liver (just like alcohol) and that processing determines where those “calories” ends up. The Biochemistry Video that explained this; explained that if various minerals, proteins were unavailable – the output from processing by the liver – simply moved 80% of the calories (HFCS) consumed straight into Fat Deposits, regardless of whether these calories were over or below your needed daily intake.
    So a calorie is not simply a calorie – and the type of calorie makes all the difference to the body.

  5. Great article thanks.

    I also think its easy for people to fall into the trap of trying to lose weight instead of trying to lose fat. I like to think about minimising fat depositing rather than burning fat because you are always burning fats, the best way to get lean is to stop storing new fat! I believe that minimising insulin response is the key and everything you said is true, its just about eating whole unprocessed food and limiting simple/fast-acting carbs.

  6. Yes the body is complex and the Calories In Calories Out model may be conveniently simple but it is nearly useless.

    The body is not a mechanical machine; as soon as you throw life into the equation, material mechanical models break down.

    4 Decades ago, I majored in Food Science and Food and Nutrition in college. One of our ongoing junior senior projects was to keep track of our caloric consumption and caloric expenditure over two years!

    What was amazing was how steady my weight was even when I was consuming enough calories to pack on some pounds. And vice a versa, substantial calorie deficits built up overtime led to nearly no weight loss.

    The conclusion we derived as Nutritionists was that a HEALTHY body will not pack on the pounds when given excess calories. It just eliminates what it does not need. And the corollary, a HEALTHY body will respond to calorie deficits and do its best to preserve its current composition. Of course there were a few exceptions to this (outliers) but the majority of students experienced fairly steady weight regardless of what or how much (within reason especially on the restriction side) they ate.

    Now granted, this was the early 1970’s. In my observation, food was healthier back then. People were more active and healthy. The processed food revolution was just beginning. The demonization of fat and the deification of grains (carbs) trends hadn’t had the time to inflict the disastrous generational consequences like they have today.

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