The scientific approach to calculating maintenance calories

Thursday, March 30, 2017. Author Nathan West

Simply put, maintenance calories are the number of daily calories required to maintain your current body weight and body composition (the proportion of fat and muscle) for a given level of physical activity. If you ate this number of calories for a prolonged period and didn't intensify your training, overreach, force adaptation or increase/decrease your activity levels, then your current body weight and body composition would not significantly change.

Why is it important to know your correct level of maintenance calories? There are a number reasons, but since I am a scientist, I’ll compare it to conducting an experiment.

Finding your baseline

During my Ph.D., I spent countless hours in the lab growing cells in flasks. These cells had been genetically engineered to produce a specific protein (sometimes of medical value) and we wanted to see if we could make them produce greater amounts of the protein1. This was attempted via several different ways through both genetically engineering the cells as well as modifying the growth media or the temperature in which the cells were grown. To see if our changes made a significant difference, we needed a baseline for comparison. This was the control condition and without the baseline, any results we got would be almost meaningless in the sense that we wouldn't know what affect the changes we made had on the protein produced.

Your maintenance calories can be deemed the baseline or control condition and knowing this number will allow you to make changes to your diet and activity levels to assess the effects on your body. However, unlike in the lab where we could set up controls every time we did an experiment (in parallel), there is only one of you (or me), and we therefore can't both run a dietary control and make changes at the same time. This means we should all invest some time working out what our daily baseline (maintenance) caloric requirement is before we start making changes.

Using your nutrition calculator

As part of the FitnessGenes "Action Blueprint", there is a nutrition calculator to compute maintenance calories. Clients are advised to start with the estimated daily calorie value while keeping their activity levels the same and monitoring their weight to see if it changes. On the nutrition calculator, there is a slider to let customers increase or decrease their calories in case the first estimate is not quite right. All equations used to produce daily calories are never 100% accurate and can only produce estimates as they cannot account for the all the different activities people do during each “typical” day (e.g. – do they sit at a desk all day or work on their feet, do they fidget a lot, do they walk upstairs at work, do they commute by walking or cycling etc.).

Therefore, there is the option for customers to select a value between -10% to +10% of their estimated daily maintenance calories. If they are gaining weight on their estimated daily maintenance calorie number, then they should reduce the value, and if they lose weight they should increase it. This process can take a few weeks to complete (2-4 weeks) but once you have a baseline calorie value, you can make small changes in your diet or activity levels and monitor the effects on your body.

Once maintenance calories are known, many people choose to try to build muscle or to lose body fat to achieve their physique goal. Both goals involve an increase in physical activity but they will involve the opposite in terms of daily calories. Losing fat will require a calorie deficit while building muscle almost always requires a calorie surplus.

Controlling variables

When conducting an experiment, you do not want to change too many variables at the same time. If a significant effect was observed, regardless of whether this was positive or negative, changing too many variables simultaneously makes it difficult to determine which variable change had the biggest impact. The duration of an experiment can also impact results. Typically, our experiments lasted between 48 hours and 5 days. If I ran the experiments for just 24 hours instead, this often wouldn't be long enough to see an effect from the variable changes. In most cases, it wasn't until after 48 hours when we could see the effects of the variable changes.

The same goes for dieting to lose body fat or to gain muscle. Often people are very enthusiastic at the beginning of a diet or exercise plan and make numerous changes simultaneously. Without proper genetically tailored advice, they might decide to drastically cut carbohydrates or fats, consume a bucket load of supplements, eat in line with the lunar phases, swap LISS cardio for some new buzzword hybrid HIIT session, swap their upper/lower split for some crazy micro-undulating periodized 'Bro' split where triceps and traps can only be trained on days of the week containing a 'T'. They soon become overwhelmed trying to adhere to and fit all the changes into their lifestyle and have no idea which change is having a positive impact or which is having a negligible or negative impact. Ultimately, the result is rather predictable: using this haphazard approach, they make little progress, get frustrated and give up.

Monitoring changes

Even if people are sensible and only make one initial small change, like reducing daily calories by 200-300 kcal or doing a couple of extra LISS cardio sessions each week, they often do not wait long enough to see if there is an effect on their body weight or other body measures (e.g.- waist or chest circumference etc.). They are impatient and often begin to make changes after only a week or a few days and repeat this until they are in a situation like the previous paragraph where they are confused and have no idea what is having a positive impact and what is having a negligible/negative impact.

Men should wait at least two weeks after making a small change to see its impact, while women might need to wait longer depending on how their menstrual cycle affects their bodies (2-4 weeks). Be patient with your transformation and make sure you give the changes time to take effect before making further adjustments.

Making continuous progress

If you've successfully dropped a dress or pant size or you've put on a few pounds of lean mass, what do you do next? It’s time to find your new baseline or maintenance calorie requirement.

Back to my cells in the lab. Sometimes after engineering the cells, we found we had successfully and permanently improved their protein production compared to the previous control conditions. This new cell would then be taken as the new baseline/control, as we again tried to further improve protein production.

The same goes for you. Once you've achieved your desired body weight or body composition, you don't need to continue eating in a calorie surplus or deficit but you do need to find your new level of maintenance calories. FitnessGenes customers can again use the nutrition calculator in their "Action Blueprint" by inputting their new weight and making slight adjustments where necessary. If they maintain a consistent level of physical activity and stick to this number of calories, then they should be able to maintain their positive body changes (except for those who have become excessively lean or those that have been using drugs to aid fat loss or muscle gain). If they do choose to make further changes to their body, then they can use this new maintenance calorie value as the new baseline.

Making significant changes to your body takes significant time. Significant changes require months and years not days or weeks, and will involve cycles of trying to induce change followed by maintenance periods before trying to make further changes. Being patient, working from a well-understood baseline, and only making small, singular changes will really aid you in reaching your goals. Treat your body as a well-controlled experiment and you will gain a much greater understanding of it as well as achieving a higher level of success.

Learning from your (and my) mistakes

As the last point, due to our egos, many of us need to learn from our own mistakes! The progression for a Ph.D. in the UK often goes like this: 1st year – believe you're going to produce the best Ph.D. project ever seen and fly out of the starting blocks ignoring the advice of more senior lab members (normally the post-docs). In reality, you realize you're not going to be winning a Noble prize anytime soon and that you have in fact spent a year repeatedly messing up experiments and not making progress. However, some of the advice you were given by the post-docs has sunk in and you begin learning from your mistakes. 2nd year – you've really started to understand your project and start making more and more progress. 3rd year – you can now carry out your experiments properly so that they soundly investigate the hypotheses you're testing and you can produce publishable results. This is analogous to a body transformation journey. Even the best bodybuilders, physique or bikini competitors and fitness models will tell you they made all sorts of silly mistakes when they first started out but learned from them.

Whatever your fitness goals, FitnessGenes is here to help you along your journey! The FitnessGenes advantage is knowledge…..and applying that knowledge to minimize guesswork, minimize mistakes and shorten the cycle to help you stay motivated and get results.


1. Pybus LP, Dean G, West NR, et al. Model-directed engineering of “difficult-to-express” monoclonal antibody production by Chinese hamster ovary cells. Biotechnol Bioeng. 2014;111(2):372-385. doi:10.1002/bit.25116.


If you enjoyed this article, you can find my other blog posts here:

How food affects your mood

What type of body fat do you carry?

Smart goal setting

Saturated fat and genetics

7 rules for sustainable weight loss

The quantified self

3 Easy Ways You Can Get Started

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