The worst foods for your metabolism

Emma Thornton
Qualified Nutritionist (BSc, MSc, RNutr)
Ask Emma

02 November 2018

Is your diet slowing down your metabolism?

Your metabolism is extremely important when it comes to maintaining healthy energy levels which is why one of the main symptoms associated with having a slow metabolism is fatigue. You see, when we speak about metabolism we are, in fact, referring to a collection of chemical processes. The main one however, is the role metabolism has in converting food into fuel for your body to use. 

If your metabolism is sluggish this means your energy levels are going to be a bit lacklustre, plus it can also impact how you lose and gain weight since your body will be burning through food at a slower rate. The good news is that there is plenty you can do to help boost your metabolism and one of the biggest things that can help is maintaining a balanced healthy diet. 

The foods you eat will be metabolised in very different ways but ideally you want to be eating foods that can give your metabolism a real workout – fibre, protein, healthy fats and carbs are good here as they force your body to burn more energy whilst breaking them down. Foods that don’t challenge your metabolism in this way often aren’t as satiating and can influence your blood sugar levels, causing your body to store more fat.

In my blog, ’15 foods to increase your metabolism’ I talk a bit more about the types of foods you should be aiming to include in your diet however, today I’m going to shake things up a bit and discuss the types of foods you should be avoiding if you want to keep your metabolism in tip-top condition!


Despite many of the rumours circulating around red wine, generally alcohol still ranks pretty low in terms of its benefits for your overall health and wellbeing. Since your body cannot store alcohol as it can with other foods such as carbohydrates, fats and protein, your metabolism has to prioritise breaking this down first. This means that, at least initially, alcohol actually speeds up your metabolism but don’t’ get to excited just yet!  If your body is busy metabolising alcohol it means that everything else – all the fats, proteins and carbs you’ve consumed that day – get shoved on to the backburner and your body won’t be able to metabolise these as efficiently, potentially leading to weight gain and other unhappy symptoms!

Vegetable oils

When it comes to choosing an oil to cook with there’s so much conflicting information out there that it can easily become confusing. Vegetable was at one time considered to be a healthier alternative however, when it comes to your metabolism most vegetable oils can take a toll. One reason for this is that they don’t provide the right balance of omega fatty acids and instead tend to be extremely rich in omega-6 fatty acids. In the right amounts, omega-6 fatty acids can actually be very good for your health but they need to be consumed in the right ratio to omega-3 fatty acids for you to get the full benefits. If you’re consuming too many omega-6 fatty acids it can contribute to inflammation which can impact your metabolism.

Processed soy

If you’re choosing to follow a meat-free diet don’t fall for the myth that all vegan foods and substitutes are innately healthier than their animal-derived counterparts. A vegan-friendly ready-meal probably contains just as many additives as a meat one - believe me, vegan chocolate cake is loaded with just as much sugar as the traditional stuff! It’s with this in mind that we should approach processed soy, a component often found in vegan alternatives, with caution. In high enough amounts process soy can upset your thyroid gland which helps to regulate your metabolism.1 That’s why, instead of opting for pre-packaged or frozen foods, it might be better to make them from scratch yourself!


You know what the real enemy of your metabolism is? Sugar! Unfortunately, not only can sugar cause fluctuations with your blood glucose levels and make you more prone to insulin resistance, it also helps your body to store fat. This is because when your body releases too much insulin it can send a signal to your fat cells, spurring them to store more fat from your bloodstream which then slows down your metabolism. These days sugar can lurk in unexpected places and while granola might be advertised as a ‘healthier alternative’ most supermarket brands are loaded with sugar – not the best way to kick-start your day! If you are interested in making granola, the best way might be to do it yourself – you could try our Orange & Vanilla Granola recipe

Refined carbs

Similar to granola, refined carbohydrates can cause mayhem for your metabolism. Unlike their complex counterparts, refined carbs have been stripped of most of their nutritional value and are instead rich in sugar which is easily able to meddle with your blood sugar levels. They also lack fibre which is a real shame as fibre can actually help to give your metabolism a boost as it’s harder to breakdown. This gives it a better workout when compared to simple carbohydrates which are easier to metabolise and so encourage metabolism to become lazy. 

Fizzy drinks

 If you’ve read my blog, ‘Could fizzy water be making me fat?’ then you’ll already know all about my feelings concerning carbonated drinks. Not only are most of them chockfull of sugar and artificial sweeteners, studies have also demonstrated that fizzy drinks can actually increase your appetite, making you more likely to binge on sweet treats after drinking them. This isn’t all though – researchers are now finding that drinking fizzy drinks may alter how your metabolism works, changing how your muscle cells utilise energy, making you more likely to store fat.2 

Non-organic meat

Meat can be quite beneficial for your metabolism as it’s full of protein which forces your metabolism to work harder. However, lean, organic meats are your best option here as non-organic meat may contain traces of chemicals such as antibiotics which may alter your gut flora. This can be problematic as some preliminary trials have found that a poor balance of gut bacteria may influence how your metabolism works, possibly leading to weight gain.3  That’s why if you are eating meat, organic is always best! 

How can you support your metabolism?

Okay, so these are the foods that could be contributing to a sluggish metabolism but this then raises the question, what can you do to support your metabolism? Well, I’ve spoken a little bit about the role that your diet plays in bolstering your metabolism and I do discuss this further in my blog, ’15 foods to increase your metabolism’ but is there anything else you could be doing?

Eat regular meals – When it comes to losing weight, a lot of people subscribe to the philosophy that ‘less is best’ but this can be disastrous for your metabolism. If you’re not eating regularly, your blood sugar levels will start to dip and your energy levels will definitely crash. You also have to consider that if you’re not eating regularly your metabolism won’t have that much to do so it will naturally slow down. When you finally do eat again, your body may into survival mode and these calories will be stored as fat – not ideal for a healthy metabolism! 

Don’t be fooled by low fat alternatives – Low fat options are all the rage these days but are these products really any healthier than the full fat alternatives? Well what they lack in fat they often make up for in sugar - not good news for your blood sugar levels or friendly gut bacteria! A balanced intake of healthy fats is actually extremely important when it comes to supporting your metabolism, so don’t start cutting calories unnecessarily! 

Get a good night’s sleep – Sleep is vital for every area of your body and if you’re not getting enough, you’re definitely going to feel the effects. Not only can sleep deprivation leave you more vulnerable to unhealthy food cravings, it also makes you less able to monitor your blood sugar levels. This combination can play havoc with your metabolism so if you want to keep things ticking over nicely, try to get at least 7-9 hours a night!

Support your gut – Your gut is extremely important when it comes to breaking down and metabolising your food so you really should be taking steps to support your friendly gut bacteria. You can do this by including more probiotic foods in your diet (think fermented – sauerkraut, kimchi and kefir!) and by utilising a prebiotic and probiotic combination. A gut-friendly prebiotic such as Molkosan can help to create the right environment for your friendly gut bacteria whereas a good probiotic like Optibacs provides just the right strains to help keep your insides happy. 

Keep your thyroid healthy – When it comes to your metabolism, your thyroid gland is pivotal – you need a healthy thyroid to secrete T3 and T4, two hormones that are crucial for your metabolism. If your thyroid isn’t producing these hormones, then your metabolism will slow down. One way you can support your thyroid is by looking at your intake of iodine. This nutrient often gets overlooked but actually plays an important role in manufacturing both T3 and T4.  You can increase your intake of iodine with nutrient-rich foods such as kelp or seaweed but if neither of these options sound particularly appetising you could try our Sea Kelp Tablets which are rich in naturally occurring iodine. 




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