It’s not as simple as calories in vs calories out

Raise your hand if you’ve ever downloaded My Fitness Pal or another calorie tracking app? Odds are you have because for a long time we’ve been lead to believe that weight loss is as simple as calories in vs. calories out. Burn more than you eat and you’ll lose weight. Sadly, if it were that simple we might not be in the midst of an obesity epidemic. 

We eat more than we say we do

The aim with weight loss is usually to be able to judge accurately how many calories we are taking in, but that involves being able to accurately record how much is being eaten. If you’ve ever studied the back of a packet of cereal, rice or pasta for example, you’ll notice there’s always recommended portion size along with the nutritional information and caloric intake for that portion size. It’s all too easy to assume that what you’ve just eaten is the recommended portion size, because, well it was just an average portion...Well these recommended portion sizes have stayed the same for a long time - but we’re eating more than ever so it’s more than likely that you’re eating much more than you think. 

Another problem is that we don’t have data available for every single food type. So if you are using a meal tracker and you’ve gone rogue and eaten a niche superfood or exotic ingredients, chances are you wont be able to find out any information on what you’ve consumed. Even when data does exist, we can’t assume that it’s representative of what’s been eaten, the potential difference between brands, methods of processing, farming techniques, origin and even seasonality and ripeness play a part too. 

Not all of the energy in food is absorbed

This is perhaps a point that you may be familiar with, and it’s a really good one to remember if weight loss is your goal. Foods that have high water and fibre contents contain less ‘metabolizable’ energy that say, a dense carbohydrate food like some bread or pasta or a piece of meat or fish. What recorded on food labels is the metabolizable energy, i.e. the amount of that food that can be successfully turned into energy. The gold standard (which, as it happens was determined over 100 years ago), is that for every gram of fat there are 9kcal, alcohol is 7kcal/gram, protein 4kcal/g and carbohydrate also 4kcal/gram. These numbers however, are still not foolproof because the amount of energy gained from them is still dependent on how readily digestible they are. So, as you can see...the picture is becoming fuzzier and fuzzier. 

Thermogenic effect of food

Just like walking requires caloric spend, so does digestion, absorption and transportation of food and nutrients. Different foods have different thermogenic effects - the energy cost of breaking down protein, for example, could but up to 25% of that protein whereas for fat it is only 5%. So by eating a lean source of protein over a spoon of peanut butter you are not only ingesting less calories to begin with but your body uses more calories in breaking it down and digesting it. 

Gut bacteria

The field of study into our gut microbiome is still new and exciting but recent studies have suggested that the different types of gut bacteria that we all have drastically influence our overall weight, likely because of the effect that our gut bacteria has on the digestion of food. One study examined the gut bacteria in 77 pairs of twins, one of whom was obese and one of whom was not. The study found that the twin that wa sobese had different gut bacteria  than their non-obese twin and more often than not the obesity was associated with a lower diversity of gut bacteria. We can increase the diversity of our gut bacteria by including lots of different fibrous plant foods, especially prebiotic foods like onions, leeks and garlic, and by eating fermented foods like sauerkraut and kimchi which contain naturally occurring probiotics. 

In conclusion calories in vs. calories out is not as black and white as we once thought it was. In terms of weight loss specifically, it’s still a viable option for most people but if you find yourself on a plateau then it might be time to address your gut microbiome, the types of foods your eating and your portion sizes. 


This article was contributed by @gracekingswell, Nutritional Therapist D. N . Med 

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