The stealth ingredient to boost your body’s ability to burn fat, all day long


Ever heard of leucine? Neither had we. That is, until nutritionist and dietitian Susie Burrell shared the benefits of this amino acid. When it comes to fat loss metabolism and muscle growth and repair, she makes a compelling case for consuming more. 

Whenever conversation turns to fat loss, certain foods and nutrients are frequently mentioned as those which should be targeted in the diet – including protein, dietary fibre and most recently probiotics.

Less frequently discussed is the biochemistry that explains the link between the foods and increased fat metabolism. One such nutrient, leucine, received significant attention in the fat loss space several years ago, after researchers identified that a certain amount of the amino acid played a key role in regulating insulin levels.

So what did this research show – what is leucine and where do you find it and will consuming more of it help you too to shift body fat? Everything you need to know about leucine is right here…

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What is leucine?

Leucine is one of the 20 amino acids, the building blocks of protein in the body. Specifically leucine is an essential amino acid, meaning that it cannot be made the body, and must be consumed in the diet. Leucine is also one of the three amino acids known as ‘branch chain amino acids’. Leucine plays a key role in muscle growth and repair and as such is of interest for body builders and recreational athletes interested in gaining lean muscle tissue.

What does it do?

All 20 amino acids are involved in protein synthesis in the body, and play roles in growth, digestion, energy production and immune function. But leucine in particular, has been shown to play a key role in regulation insulin and glucose metabolism in the body. As insulin is the central regulator of fat metabolism, it is believed that the leucine content of the diet, in turn helps to support fat being burnt as energy whilst ensuring muscle mass is preserved, even when calorie restricted diets are followed.

Can leucine increase fat loss?

To date there is no evidence to show that a diet high in leucine specifically results in greater weight loss when following a particular diet. What the research does show, generally in rat studies, is that diets with a higher leucine content helps to increase the amount of fat lost, and increase amount of muscle mass protected, compared to diets with a lower protein and leucine content, whilst also improving the action of insulin in the body. As insulin plays such as powerful role in fat metabolism, over time it is believed this helps to prevent weight regain over time.

There is though much scientific evidence to show that higher protein diets are effective in achieving sustained weight loss over time, and this may be somewhat explained by the higher leucine content of high protein diets.

How much leucine do you need?

Leucine is found in greatest concentrations in animal based foods including eggs, chicken, milk and beef and studies to date have suggested that two to three grams of leucine is a target amount to aim for in each meal to optimise leucine intake.

In food terms, this can be found in two eggs, 25-30g Whey protein powder, 150g of lean beef or chicken or 250 of Greek yoghurt. In plant foods it is trickier, with 12 slices of wholemeal bread required to give two grams of leucine; although one cup of whole grains, such as oats or legumes offers roughly one gram of leucine.

The take home message

As we learn more about fat metabolism, we also learn about the biochemical pathways that determine if fat is stored or burnt in the body. While more research is needed, findings to date suggest that if your goal is fat loss, and especially if you have insulin issues, aiming to consume two to three grams of leucine at each meal and snack is an easy way to help ensure your body has access to the amino acid it needs to support insulin regulation over time.

As insulin issues are increasingly common, and as insulin tends to increase as we get older, move less and gain weight, keeping your insulin levels tightly controlled over time is a smart thing for us all to do – for both our health and weight control long term.

Susie Burrell is a dietitian and nutritionist. Continue the conversation on Twitter @SusieBDiet.

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