For most people, a calorie deficit of between 500–1000 calories per day is perfectly healthy, provided you’re not already a healthy weight (or underweight) and that the deficit isn’t sustained for extended periods of time.
This is a blanket rule, but the real answer is a little more nuanced…
Getting into a calorie deficit consistently, over a long period of time is the key underlying principle of fat loss.
That means it’s impossible to lose fat if you’re not in a calorie deficit, regardless of what you do or don’t eat (that’s right, Keto only ‘works’ if you’re in a calorie deficit).
The problem is, as soon as people hear about this, they’ll start eating 500 calories a day.
Will that put you in a deficit? Yes, almost definitely (unless you’re a very small, light child)
But is that a healthy deficit?
If you’re not eating in a healthy, sustainable deficit, you’ll end up hungry, lacking in energy, demotivated, and after a couple of weeks, you’ll quit and go back to what you were doing before, and then again back of the weight you lost.
You’ll convince yourself that a calorie deficit doesn’t work and go back to yo-yo dieting and perpetually spinning your wheels when it comes to weight loss.
But is being in a calorie deficit healthy?
IS A CALORIE DEFICIT HEALTHY?
This depending on your current weight and how big of a calorie deficit you choose to undertake, but let’s look at this question in relation to different categories on the BMI scale (yes, the BMI scale isn’t the best measure of what’s healthy or not because it doesn’t take muscle to fat ratio into account, but it gives us some broad guidelines to work from).
UNDERWEIGHT: For people who are underweight, a calorie deficit is likely neither healthy or necessary
HEALTHY WEIGHT: People who are at a healthy weight might choose to be in a deficit to lose a small amount of weight, but the deficit should be conservative (maximum of a 500 calorie deficit per day).
OVERWEIGHT: Of course if you’re overweight then it’s probably a good idea to get yourself into a calorie deficit so you can start to work towards being a healthy weight. For these people, I’d recommend around a 1000 calorie deficit per day.
OBESE: it goes without saying that if you’re obese, your health depends on you being in a calorie deficit, in fact, NOT being in a calorie deficit would be unhealthy for this group. For anyone in this group, I’d recommend a calorie deficit of over 1,000 calories per day.
So yes, in the right context a calorie deficit can be healthy, but whether or not you should be in a calorie deficit really depends on the individual and their specific situation.
HOW MUCH WEIGHT LOSS WILL EACH CALORIE DEFICIT LEVEL PROVIDE?
Bigger calories deficits mean more weight loss.
If you’re in a large deficit for a long period of time, then you’ll lose more weight, more quickly.
Smaller deficits and shorter periods of time spent in that deficit will produce slower, smaller amounts of weight loss.
This is how much you could technically expect to lose with different sizes of deficit.
|DAILY CALORIE DEFICIT||WEEKLY CALORIE DEFICIT||ESTIMATED WEEKLY WEIGHT LOSS (Kg)||ESTIMATED MONTHLY WEIGHT LOSS (Kg)||ESTIMATED WEEKLY WEIGHT LOSS (Lb)||ESTIMATED MONTHLY WEIGHT LOSS (Lb)|
SO WHAT IS A HEALTHY CALORIE DEFICIT FOR WEIGHT LOSS?
Again, this really depends on a lot of factors and comes down to what you want to achieve and how quickly you want to achieve it, but as mentioned earlier, somewhere between a 500–1000 calorie deficit per day is going to be ideal for most people
This will produce roughly 1-2lbs or 0.5-1kg of weight loss per week.
So, if you currently weigh 90kg and you want to lose 10kg, a deficit of 500 calories per day will get you to your target weight in around 20 weeks (5 months), a deficit of 1000 calories per day will get you to your target weight within 10 weeks (2.5 months).
In reality, you should probably aim for the longer-term end of the scale because weight loss is never plain sailing and is a little more nuanced than a simple mathematical equation.
Life events like holidays, weddings, work parties, meals out, and drinks with friends will inevitably mean that you’ll be in a calorie surplus, or at least at maintenance for periods of time, which will mean your desired level of weight loss will take longer to achieve.
For this reason. It’s important not to put too much pressure on yourself and aim for a more conservative time period to get the weight off
WHAT ARE THE RISKS OF A LARGE DEFICIT?
I mentioned earlier that very large deficits (1,500+ calories per week) are going to be mentally tough to maintain because of the high levels of restriction and the resultant hunger.
Many people believe however that there is a physiological process that occurs when a large deficit is in a place called ‘starvation mode. The theory is that to compensate for a lack of calories the body will slow down your metabolism and weight loss will stop (some people even believe you’ll gain weight).
Starvation mode is a myth. As you lose weight metabolism will decrease, but this is a natural and gradual process – a smaller body needs fewer calories to keep itself alive and move around so of course metabolism will reduce.
So while this shouldn’t be a concern, large calorie deficits may result in general lethargy, tiredness, an inability to exercise effectively, and an inability to focus mentally.
All of this will of course impact your adherence to a diet, and if you can’t adhere, you won’t lose any weight, so stick to a moderate deficit!
Aside from the mental struggle, however, large calorie deficits can be physically damaging. Some of the risks include;
1. A DECREASE IN MUSCLE MASS
Extreme, fast weight loss can mean losing substantial muscle tissue as well as fat. This is something that will have a material impact on metabolism, independent of total body weight.
If you two people of the same bodyweight, one with more muscle; the one with more muscle will generally have a higher metabolism.
Muscle tissue = good.
Do everything you can to eat least preserve muscle tissue, one of those things being losing weight slowly
2. AN INABILITY TO TRAIN PROPERLY
Whether you do cardio or lift weights, getting the most out of your training will be very difficult if you’re on very low calories.
Dropping your calories is the most powerful tool in your weight loss arsenal, but exercise can help too, so make sure you’re sufficiently fulled to train optimally
3. POTENTIAL NUTRIENT DEFICIENCIES
The less food you eat, the less chance you have to get all the macro and micronutrients you need for optimal health. You can of course eat a nutrient-rich diet on low calories, but it’s tricky.
Regardless of how many calories you’re, you need to ensure you get a good balance of protein, carbs, and fat as well as a broad range of vitamins and minerals.
We all want to lose weight as quickly as possible, but by doing so, the likelihood is that you’ll be shooting yourself in the foot.
Use a moderate calorie deficit of between 500-1000 calories per day, stick with it and be patient.
Aim to lose roughly 0.5-1kg per week (1-2lbs) on average and you can’t go wrong.
Joe is an online weight loss coach and qualified personal trainer of 15 years who helps busy, professional men and women lose fat and build muscle.
Having a 9-5 desk-job, Joe understands the struggles of juggling a hectic life with trying to maintain a good physique.