Your body needs fat – why being lean isn’t all that

There’s an obsession with leanness in the fitness industry that is not so healthy. 

People are dieting to, or trying to diet to, extremely low levels of body fat that can have some fairly negative side-effects. 

Here are 8 downsides to being super lean: 


1. You’re always cold 

Fat helps to insulate your organs and regulate your body temperature. Not enough body fat and you’ll find it harder to stay warm. 

2. Decreased performance 

If you’re super lean, your body doesn’t have stored energy to draw on. This means that once you’ve depleted your glycogen stores, your training performance will suffer. It will also hinder your recovery, meaning you won’t be getting the best out of your sessions. But it’s not just your performance in the gym that suffers…


3. Your hormones go haywire

Having very low levels of body fat signals to your body that you aren’t healthy enough to reproduce so your body disrupts the production of testosterone, progesterone, and oestrogen, which can lead to a host of issues, including low libido. 

4. You stop getting your period

Women in particular need around 25-30% body fat for normal hormone production. If this gets disrupted by dieting to low levels of body fat, those with menstrual cycles may notice they stop getting their period (called amenorrhea). If you lose your period or start getting irregular periods when you are dieting for fat loss, you should speak to your GP as soon as possible. 

5. Brittle bones

At low levels of body fat, it’s harder for your body to properly absorb and use vitamin D and calcium.  Coupled with the changes to testosterone and oestrogen, which assist with bone turnover )so basically, old bone breakdown will exceed new bone development), you’re at a much higher risk of osteoporosis and stress fractures. 

6. Brain fog

When your body is running low on energy stores, it’s using what it has to keep your vital organs running. In order to do this, it slows down your brain function to conserve energy, so you might have difficulty concentrating or notice memory issues. 

7. Constipation 

Speaking of your body slowing down… One of the processes your body slows down when it’s running low on energy is digestion, which can leave you feeling backed up. 

8. Life is less fun 

In order to get to, and maintain, low levels of body fat, you have to make certain sacrifices. This often means eating out, consuming alcohol, and social events are cut out so you can have greater control over your calorie intake and have more time for the training you need to do to get to these levels of leanness. 


Even though extreme leanness is used to advertise fitness, it’s not actually the epitome of health it’s made out to be. Maintaining healthy levels of body fat will help you function and train at higher levels, while still enjoying a bit of a life outside the gym.  

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