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We know that Eating too much is bad.


If you eat more calories than you burn, you gain weight. (You’re in a calorie surplus) but when you’re dieting and trying to lose fat, eating too much just doesn’t cut it.


You may not spend every single day of your diet in a calorie deficit (if you’re including re-feed or high carb days) but on the whole, you need to be eating less than you consume.

So if we need to eat a little less to lose fat, then eating a lot less will mean we lose fat faster, right? Will we get leaner quicker?

Not at all, under-eating can be just as detrimental on your physique as over-eating.


Here are a few reasons why


Losing Mass

The idea of a diet is that you eat in enough of a deficit that your body has to tap into its stored fat to burn for energy, but your deficit isn’t so large that you have to burn off muscle.

Your body would prefer to hold on to its lean mass, but it can only burn fat at a certain rate, and if your deficit is too large, you will start losing size.


Dropping Strength

While your strength may take a dive during a diet, simply due to the fact that you’re in a deficit, or your leverages are getting worse, and there’s less cushioning around your joints as you’ve dropped fat, strength shouldn’t take too much of a hit … unless you’re under-eating.


Lack of Dietary Adherence

This is the biggie. It’s also the reason why many people following extremely low-calorie diets tend to plateau or even put weight on.

People think they’re only eating 1,000 or 1,500 calories per day, and then wonder why they can’t seem to lose weight. Actually what they’re doing is probably sticking to this five or six days per week, and binging on the other days. This is a huge issue for many dieters.

By dropping your calorie intake right down, you make yourself hungrier and increase your cravings. A certain amount of these is perfectly normal on a diet, but the lower your calorie intake, the more you’ll experience hunger cravings.

In a small to moderate deficit, you can control these with willpower alone, but when your deficit is too big, willpower only stretches so far, as your body’s physiological need is for more food to help it survive. And you can try as you might but you can’t sustain yourself and ignore the cravings, so you give in and binge.

Let’s say that you do this twice a week – once on a small scale, and once with a bigger, all out binge. We’ll take the example of someone who needs 2,000 calories to maintain their weight, and is trying to stick to just 1,000 calories per day:

1,000 calories x 5 days = 5,000 calorie deficit.

3,000 calories x 1 day = 1,000 calorie surplus

6,000 calories x 1 day = 4,000 calorie surplus

Over the course of the week, those two unplanned higher calorie days bring our guy or girl’s weekly calorie balance up to maintenance level, so it’s no wonder they’re not losing weight.


Metabolic Slowdown

Your metabolism can adapt to whatever is thrown at it, so if you consistently under-eat, there’s a quantity of return.

Certain hormones will down-regulate, you burn fewer calories, and your subconscious levels of NEAT (Non-Exercise Activity Thermogenesis) decrease.

You’ll also feel tired, fatigued and irritable.


Is it ever OK to Under-Eat?

A calorie deficit could theoretically be categorised as under-eating, as you’re consuming less than your body needs.

So yes – it is okay to under-eat.

However, there’s a difference between a small to moderate calorie deficit, where you lose fat, but maintain muscle and strength and a large calorie deficit where you’ll likely lose mass, your performance will decrease, and you’re at a higher risk of binging.


For an ideal calorie deficit, you need to take between 400 and 750 calories per day away from your maintenance calorie intake.

Or, a simpler alternative is to multiply your bodyweight in pounds by between 9 and 12 for women or between 11 and 14 for men. (The more active you are, the higher the multiplier.)

If you find you’re dropping weight, but also getting weaker, feeling really run down, and losing more than 1-2% of your bodyweight per week, it’s highly likely you’re under-eating, so up those calories a little, and watch your diet get a heck of a lot more effective


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