Catherine’s calorie Calculator

The results boxes explained:

Maintenance - stay where you are.

Here, I’ve kept you at the calculated maintenance calories. These are the calories (energy) you need in order to maintain roughly the same amount of body fat. Your weight will still fluctuate within a range, since many things impact our weight, this is normal so don’t expect your weight to stay exactly the same maintenance. Your weight may even increase slowly over time if you’re also building muscle.

Smallest deficit - gentle and slow.

Here, we’ve taken 10% away from your maintenance calories. These are the calories you need to lose fat in a very gentle and slow way. Because the deficit is smaller, it means that you’ll lose fat slowly over time but the benefit is you may find yourself having to make less compromises in your food and drink choices. I don’t recommend opting for this one if you’re very impatient. But I do recommend it if you want to work on your relationship with food in conjunction with fat loss.


Small deficit - still reasonably gentle and slow.

Taken 15% away from your maintenance calories. This is still a relatively gentle rate of fat loss less so than 10% deficit. You’ll still need to make some compromises but not as many as you’d need when creating a larger deficit.

Moderate deficit - balanced and sustainable.
Here, I’ve taken 20% away from your maintenance calories. The deficit is larger than the previous options, which means you’ll lose fat quicker but will probably have to compromise more on your food choices. This is what I use with most of my clients since it’s a balance between seeing motivating fat loss, still enjoying life, and preparing for a maintenance mindset.

Larger deficit - harder and less balanced.

25% away from your maintenance calories.
 You’re going to need to be a little more serious about making compromises. You may feel hungry more often, depending on your food choices… and you may need to make sure you don’t inadvertently slack on the movement side of things. Probably best to avoid this option if your relationship with food could do with some work or you’re prone to binge eating tendencies. 

Aggressive deficit - more sacrifices, less sustainable.

Here, I’ve taken a significant 30% away from your maintenance calories. 
Here and beyond you will create faster fat loss. If you can stick to it consistently, the process of fat loss won’t last as long as other options. You’ll have to be okay with making not just compromises but also sacrifices. You’ll probably feel hungry often and have to make a real effort against inadvertently dropping your activity levels. If you’re considering this option, be realistic with how you want your life to look for the foreseeable. Unless you’re already a seasoned pro at maintenance, it’s unlikely this option will help prepare you for moving away from fat loss, thus results could be less sustainable. I’d highly recommend against this option if your relationship with food could do with some work, if you’ve tried to diet aggressively before and it hasn’t worked, or if you’re at risk of losing more muscle mass than most.

Small surplus - increasing body weight for health or muscle building.

Adding 10% on top of your maintenance calories. 
These are the calories (energy) you need to gain body fat. Some people may want to create a small energy surplus to help build muscle mass - this is generally only relevant if you’ve a few years experience in lifting weights, have already built a significant amount of muscle mass and want to shift muscle building up a gear. If muscle gain (and not fat loss) is your goal, you probably don’t need to ‘bulk’ by putting yourself into a ridiculously high surplus, your muscles will have an ‘energy cap’ - consider this a threshold at which muscle growth is saturated no matter how much more energy you give your muscles - it’s like continuing to pour water into a bucket even when it’s already full.

Now that you’ve read through some of the options, here are further considerations to help you on your way. 

Catherine’s top tips

1. However you’re measuring your fat loss (scale weight, tape measurements, progress photos or a combination of all), don’t give up and don’t drop your calories if you see no changes after one week. Stick to your calorie and activity target for no less than 3 weeks before changing anything. And even then, ask yourself if you’ve truly been adherent to your calories and to your activity target (steps).

2. The calorie estimates above rely on you consistently meeting your chosen activity level (number of steps). The number of calories you need to consume will be dictated by those activity levels over time; both sides of the energy balance equation are important and they will both impact one another.

3. If you have less body fat to lose (are already relatively lean or in a healthy BMI range), you will find that fat loss is slower. If you want fat loss to be quicker, you will have to increase the size of your deficit but this will ultimately mean making the process harder and less enjoyable. Ask yourself if you really need to lose more body fat, especially if you’re already a healthy weight.

4. The larger the deficit you create, the more likely you are to lose muscle mass and muscle mass is incredibly important for good health, lowering the risk of disease wellbeing, functioning in everyday life, and independence later in life. Therefore, whichever calorie option you choose, I’d always recommend you eat plenty of protein and regularly exercise including lifting weights.

5. When you’ve lost the fat you want to lose, go back to maintenance calories, you can’t be in a deficit forever. Your new maintenance calories will be a little less than before you lost the fat, this is because you’re now a smaller and more efficient person who needs to use up less energy to move around. That’s a normal byproduct of fat loss, you haven’t broken your metabolism or unbalanced your hormones.

6. You’re not as physiologically different to the majority of people as you think (sorry!). There’s no need to be eating less than 1,200 calories a day, unless perhaps you have a medically diagnosed thyroid or other metabolic disorder. For most people opting for a small-to-moderate deficit (15-20%) is far more sensible than dropping calories drastically to figures such as 30%, 40% or even 50%. This makes sense since it helps prepare you for the mindset and behaviours needed for maintenance, when you eventually get there.

7. Contrary to popular belief, the biggest barriers you’ll face will usually be around changing your behaviours and being consistent for long enough to see your hard-earned results, whatever your goal - it won’t actually be about finding the exact right calorie target or workout regime. 

Fat loss shouldn’t be about losing fat as quickly as you can and making yourself miserable and resentful in the process, you also want to enjoy your life and furthermore maintain your hard work, right?  

If you want some help to simultaneously change your behaviour, stay consistent, see results and enjoy life… get in touch with me. I promise I’m very friendly, and helping people like you is what I do.

Catherine