Why a low carb diet is doing more damage than good to your waistline

Turns out your body needs a certain number of carbs to be able to metabolise foods. So if you’re not in ketosis, low carb diets can actually halt your weight loss.

Poor old carbs have been off the menu on many a diet for a number of years, with a range of programs including keto, Atkins, The Zone and range of shake based diets significantly reducing or even eliminating bread, rice, cereal, pasta, sugars and even fruit as their default recommendation.

While extremely low carb, or very low calorie diets, as well as keto, will result in relatively fast weight loss when they are rigorously followed, there is also a less frequently discussed downside of significantly reducing your carbohydrate intake.

In this scenario, chronically low carbohydrate intakes can significantly impact metabolism, especially for active people, which ultimately makes weight control more and more challenging over time.

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So, if you have been a frequent follower of low carb diets, yet fail to see any real, sustainable results, these are the reasons why consuming too little carbohydrate can be just as bad as consuming way to much when it comes to optimising metabolic rate.

What are carbs and why do I need them?

Carbohydrate rich foods include plant-based foods such as starchy veggies, fruit, grains, cereals as well as simple sugars like honey and sugar.

Carbohydrates are digested in the body to give glucose, which is the primary fuel for the muscles and for the brain.

A common weight loss strategy is to reduce overall carbohydrate intake to help increase the amounts of fat required for energy, and to support weight loss.

More extreme low carb diets include keto, in which carbohydrate intake is as low as 20-30g each day, or less than 10% of total energy result in ketosis.

In this state carbohydrate intake is so low, the body is forced to breakdown fat and form ketones which act as an alternative fuel source for the brain and the muscles.

The low carb diet confusion

While inducing ketosis can be an extremely effective way to lose weight quickly, in reality it is not so easy to do, nor maintain long term.

A much more common scenario is one in which carbohydrate intake is reduced, with the elimination of cereals, grains, fruit and starchy veggies, but not so low as to induce ketosis. Metabolically the body needs a certain amount of carbohydrate to burn body fat.

This means that it is possible to be consuming carbohydrate, but too much to achieve ketosis and too little to adequately fuel the muscle and support fat metabolism. Typically, this occurs when someone exercising regularly drops their intake of carbs to 100g or less.

Initially such a reduction in calories results in 2-3kg of weight loss before this completely halts and no matter how much more exercise, or how little they eat, the scales refuse to budge.

It also explains why someone who has had success with a low carb diet initially regains weight again quickly when carbohydrate is reintroduced. To make matters worse, each and every time carbs are slashed again in an attempt to induce weight loss, it becomes more and more difficult to lose weight. Basically, the body has lost its metabolic efficiency, after being starved of its primary fuel repeatedly.

What does this mean?

If you are someone who has regularly cut carbs to lose weight, and find it no longer seems to work, it is a sign that your carbohydrate intake may simply be too low for your level of physical activity.

Generally speaking, total carbohydrate intakes lower than 100g per day, for those who exercise regularly and only have relatively small amounts of weight to lose (5-10kg), are too low, and increasing your intake to 120-160g or at least 30-40% of total calories may be what your body needs to metabolise fat when your calories are reduced.

This amount of carbohydrate overall is a moderate intake, and a prescription shown to give slower yet sustainable weight losses of ½ -1 a week, long term.

What else is going on?

The other less frequently mentioned issue that relates to cutting back on carbs is that often we then overdo the protein and fat by overconsuming fatty meats, cheese, avocado, nuts and high calorie keto and paleo snacks.

Here, carbs may be low overall, but calories remain too high as a result of too much fat and protein. No matter what the macronutrient makeup of the diet is, is too many calories are being consumed, weight loss will be halted.

The take home message

While we may think that we are doing ‘keto’ or even ‘low carb’, a closer look at eating habits, calorie intake and macronutrient balance will often reveal your calorie intake or even carb intake may not be as low as you think.

While our natural instinct may be to cut back on carbs, it is possible to eat too little overall and negatively impact metabolic rate long term.

A quick calorie or carbohydrate check via an online monitoring program, or a consult with an Accredited Practising Dietitian may be all you need to get both your macros and your calories on track to help you achieve your dietary and body composition goals.

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