The Truth About Low-Carbohydrate Diets

Low-carbohydrate diets have been touted as the cure-all in nutrition. However, nutrition is complicated, and one solution is not going to be the answer to everyone’s problems. So, how many of the claims about low-carb diets are true? Read on to find out.

What is a low-carb diet?

There are no firm guidelines defining what a low-carbohydrate diet is. Generally, a moderately low-carbohydrate diet consists of 150g of carbohydrates a day[1,2]. This would mean carbohydrates make up 30% of someone's 2000kcal intake a day[1]. Having said that, a diet could be considered ‘low-carb’ if it contains as much as 45% carbohydrates[3], as this is less than the 50% carbs that make up a typical Western diet[4,5]. A very low-carbohydrate, or ketogenic diet consists of less than 50g of carbohydrates per day[6]. You can find out more in our What is the Ketogenic Diet? article.

Low-carbohydrate diets can vary a lot from one to another. To achieve a low-carbohydrate diet, grains, starchy vegetables (such as potatoes), and fruits are reduced or eliminated entirely. This leads to a diet that is higher in fat and protein. Often, a low-carbohydrate diet contains animal products[7], but it doesn’t have to.

Getting enough nutrients

A low-carbohydrate diet could help to reduce the amount of highly processed, unhealthy foods eaten. This is because they tend to be high in simple carbohydrates and fat[8]. Carbohydrates and fat in the right proportion lead to foods which are high in calories, easy to overeat, and relatively low in vitamins and minerals[9]. Therefore, by reducing the amount of carbohydrates in the diet, a person may, by default, achieve a healthier dietary pattern[8].

On the flip side, eliminating foods from the diet can make it more difficult to consume certain nutrients, such as folate and iodine[10]. Another nutrient that is often seen as a concern is fibre. Fibre, while technically a carbohydrate, is non-digestible and therefore treated differently than other digestible carbohydrates, like starch. The issue when following a low-carb diet in the West is the majority of the fibre eaten comes from grains[11]. The good news is vegetables, seeds, and nuts are high in fibre whilst being low in digestible carbohydrates, so they are great foods to include in a low-carbohydrate regime. In fact, it’s been shown that a low-carbohydrate diet can provide at least the recommended amount for all nutrients,[12] but this does require a bit of thought.

Losing weight

It’s a common myth that carbohydrates are what cause people to gain weight[13]. This leads to the idea that low-carb diets are superior for weight loss.

When looking at low-carbohydrate diets versus diets higher in carbohydrates, it appears that in the short term, a lower carbohydrate intake can lead to a greater weight loss[14]. However, from six months and beyond, there is little difference in the amount of weight lost when comparing diets that vary in carbohydrates[14-16]. Part of the reason for this is that people gradually increase their carbohydrate intake over time, which results in more calories being eaten[16]. A key factor for success in these studies was adherence[16]. The better a person can stick to their chosen diet, whatever that may be, the greater their chance of reaching their goals[16].

To find out more about carbohydrates in relation to weight loss and in general, check out our article here.

Is a low-carb diet right for me?

A low-carbohydrate diet may be the right choice for some people. It’s simple to follow but like any diet, the quality of foods eaten should still be considered.

It has been shown that a low-carbohydrate diet can increase LDL (bad) cholesterol and that this effect is greater for certain individuals[17]. Therefore, it’s a good idea to keep an eye on cholesterol levels during doctor check-ups in the early stages of a low-carb diet. It’s best to aim for unsaturated fats over saturated fats, which have been shown to be more beneficial in relation to cardiovascular health[18-20].

What is more important to think about than low-carb, high-carb, or single nutrients is the overall diet[21,22]. This means focusing on the types of carbohydrates and fat being eaten, and the foods supplying them, rather than the amounts. Aiming for a whole-food, plant-rich diet is one way to achieve this.

Where does Huel fit in?

For a low-carbohydrate diet, Huel Black Edition is the most suitable Huel product. The other products in the Huel range could make up one full meal if other meals are much lower in carbohydrates, but this would require some planning. The calories in Huel Black Edition come from carbohydrates (17%), fat (40%), protein (40%) and fibre (3%). Since it contains all 27 essential vitamins and minerals, there’s no need to worry if you’re getting everything you need – it’s all worked out for you.

Most of the fats are polyunsaturated and approximately half of the saturated fats in Huel products are Medium-Chain Triglycerides (MCTs), which the body treats differently to most other saturated fats[23]. You can find out more about MCTs here.  

Low Carb Diet FAQs

What is a low-carb diet?

 While there are no official guidelines defining what a low-carbohydrate diet is, generally, a moderately low-carbohydrate diet consists of around 150g of carbohydrates a day[1,2]. This would mean carbohydrates make up 30% of someone's 2000kcal daily intake[1]. That said, a diet could be considered ‘low-carb’ with up to as much as 45% carbohydrates[3], as this is less than the 50% carbs that make up a typical Western diet[4,5]

How many carbs are in a low carb diet?

150g of carbohydrates a day would qualify as a ‘low-carb’ diet which would be approximately 30% of a 2000kcal intake.

Can low carb diets help you lose weight?

Low carb diets may result in more rapid weight loss, particularly in the early stages of adopting a regime[14]. However, over the longer term, low carb diets appear to be no more successful than any other diet, so it’s about finding something that works for you[14-16].

What should you eat on a low carb diet?

A typical low carb diet will focus on meat, nuts, dairy, fats and oils and non-starchy vegetables.

What food should you avoid on a low carb diet?

Most fruits, sugar, breads, pastas, grains, and starchy vegetables are generally avoided on a low carb diet.

Low carb diets vs keto diets

A ‘ketogenic’ diet consists of very low levels of carbohydrate - less than 50g of carbohydrates per day[6]. The aim of ketogenic diets is to send the body into a state of ‘ketosis’ through a lack of carbohydrates (ketosis is when, instead of using the glucose from carbs for energy, the body burns fats instead of carbohydrates as its main source of fuel). You can find out more in our What is the Ketogenic Diet? Article.

Do low carb diets work?

A low-carbohydrate diet may be the right choice for some people. It’s simple to follow but like any diet, the quality of foods eaten should still be considered. They can result in weight loss but it is important to make sure this is not to the detriment of health in other areas, such as an increase in LDL (low-density lipoprotein) cholesterol.

Are low carb diets healthy if you have diabetes?

Diabetes means the body can’t effectively process carbohydrates. Normally, carbs are broken down into glucose (blood sugar). When blood sugar rises, insulin is produced which allows blood sugar to enter cells and regulates the level. With diabetes, this regulation process doesn’t work, resulting in the potential for large (and dangerous) fluctuations in blood sugar.

Low carb diets can help people with type 2 diabetes manage blood sugar more effectively[24]. If you feel a low carb diet may work for you then consult your doctor or dietitian.

Are low carb diets healthy for women affected by polycystic ovarian syndrome (PCOS)?

Women with PCOS have symptoms including irregular periods and weight problems. A low carb diet which reduces insulin production may help with these symptoms and other potential complications including diabetes, high blood pressure and infertility[25]. If you feel a low carb diet may work for you then consult your doctor or dietitian.

Can a low carb diet cause headaches?

During the early stages of switching to a low carb diet, especially one that is low enough to be considered ‘keto’, you may experience side effects as the carbohydrate in your body is replaced with fat. One of these side effects is headaches, which can be as a result of several factors:

  1. Low blood sugar. The reduction in carbs will result in a reduction in glucose, one of the body and brain’s main sources of fuel. This drop in glucose will lead to low blood sugar, which can result in headaches and mental fatigue.
  2. Dehydration can also be a side effect of a low carb diet, which leads to headaches. The reason for dehydration is two-fold: firstly, your body will use its glycogen stores, and glycogen is bound to water molecules. As the glycogen is used, the water is released and expelled as urine. Secondly, fewer carbs consumed means less insulin is produced. This drop in insulin can trigger your kidneys to expel more sodium, increasing dehydration levels.

What fruits can you eat on a low carb diet?

There are lots of fruits that can be eaten as part of a low carb diet, such as watermelon, strawberries and blackberries, avocados, honeydew melon and peaches.

(If your doctor has recommended that you avoid sugar, check with them before you increase your fruit intake.)

Does a low carb diet cause constipation?

Some studies have shown that constipation on low carb diets can impact up to 50% of people[26]. However, there are ways to get around this.

As referenced earlier, low carb dieting can increase the chance of dehydration. This in turn can result in constipation, but it can often be easily dealt with by simply increasing your fluid intake.

Low carb diets also often have reduced levels of fibre, which can temporarily result in constipation. However, low carb diets don’t necessarily have to have reduced fibre. Vegetables and seeds can provide this fibre to reduce the chance of constipation.

Does a low carb diet impact your sleep?

A chain reaction in the body because of reduced carbs can cause restless sleep. As mentioned earlier, a reduction in carb intake can reduce the amount of insulin the body produces. The knock-on effect is that less of the amino acid, tryptophan, is converted by insulin into molecules used to make serotonin. Less serotonin can impact sleep patterns.

It is best to transition to a low carb diet over time, cutting out approximately 20g of carbs each day to allow your body to adjust, and reducing the chance of any undesirable side effects.

References

    1. Patel K. Does “low-carb” have an official definition? Date Accessed: 03/01/2020. [Available from: https://examine.com/nutrition/does-low-carb-have-an-official-definition/]
    2. Wylie-Rosett J, et al. Health effects of low-carbohydrate diets: where should new research go? Curr Diab Rep. 2013; 13(2):271-8.
    3. Hu T, et al. Effects of low-carbohydrate diets versus low-fat diets on metabolic risk factors: a meta-analysis of randomized controlled clinical trials. American journal of epidemiology. 2012; 176 Suppl 7(Suppl 7):S44-S54.
    4. England PH. NDNS results from years 1 to 9. London, UK: PHE Publications. 2019.
    5. Statistics NCfH. CDC. Dietary intake for adults aged 20 and over. Date Accessed: 07/01/19. [Available from: https://www.cdc.gov/nchs/fastats/diet.htm]
    6. Uppaluri WMK. Ketogenic Diet. StatPearls, (eds). Treasure Island (FL); 2019.
    7. Guess N. Dietary intake in people consuming a reduced-carbohydrate diet in the National Diet and Nutrition Survey. Journal of Human Nutrition and Dietetics. 2017; 30(3):360-8.
    8. Martínez Steele E, et al. The share of ultra-processed foods and the overall nutritional quality of diets in the US: evidence from a nationally representative cross-sectional study. Popul Health Metr. 2017; 15(1):6-.
    9. Hall KD, et al. Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake. Cell Metab. 2019; 30(1):67-77.e3.
    10. Churuangsuk C, et al. Impacts of carbohydrate-restricted diets on micronutrient intakes and status: A systematic review. Obesity reviews : an official journal of the International Association for the Study of Obesity. 2019; 20(8):1132-47.
    11. Stephen AM, et al. Dietary fibre in Europe: current state of knowledge on definitions, sources, recommendations, intakes and relationships to health. Nutrition Research Reviews. 2017; 30(2):149-90.
    12. Zinn C, et al. Assessing the nutrient intake of a low-carbohydrate, high-fat (LCHF) diet: a hypothetical case study design. BMJ Open. 2018; 8(2):e018846-e.
    13. Why Carbs Aren’t Bad. Date Accessed: 03/01/2020. [Available from: https://huel.com/pages/why-carbs-arent-bad]
    14. Guo J, et al. Objective versus Self-Reported Energy Intake Changes During Low-Carbohydrate and Low-Fat Diets. Obesity (Silver Spring, Md). 2019; 27(3):420-6.
    15. Das SK, et al. Long-term effects of 2 energy-restricted diets differing in glycemic load on dietary adherence, body composition, and metabolism in CALERIE: a 1-y randomized controlled trial. The American journal of clinical nutrition. 2007; 85(4):1023-30.
    16. Gardner CD, et al. Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion: The DIETFITS Randomized Clinical Trial. Jama. 2018; 319(7):667-79.
    17. Kirkpatrick CF, et al. Review of current evidence and clinical recommendations on the effects of low-carbohydrate and very-low-carbohydrate (including ketogenic) diets for the management of body weight and other cardiometabolic risk factors: A scientific statement from the National Lipid Association Nutrition and Lifestyle Task Force. Journal of Clinical Lipidology. 2019; 13(5):689-711.e1.
    18. Clifton PM, et al. A systematic review of the effect of dietary saturated and polyunsaturated fat on heart disease. Nutr Metab Cardiovasc Dis. 2017; 27(12):1060-80.
    19. Forouhi NG, et al. Dietary fat and cardiometabolic health: evidence, controversies, and consensus for guidance. BMJ (Clinical research ed). 2018; 361:k2139-k.
    20. Liu AG, et al. A healthy approach to dietary fats: understanding the science and taking action to reduce consumer confusion. Nutr J. 2017; 16(1):53-.
    21. Reynolds A, et al. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. The Lancet. 2019; 393(10170):434-45.
    22. Bao W, et al. Low Carbohydrate-Diet Scores and Long-term Risk of Type 2 Diabetes Among Women With a History of Gestational Diabetes Mellitus: A Prospective Cohort Study. Diabetes care. 2016; 39(1):43-9.
    23. Marten B, et al. Medium-chain triglycerides. International Dairy Journal. 2006; 16(11):1374-82.
    24. Diabetes.co.uk. Low Carb. Date Accessed: 29/04/22. Available from: https://www.diabetes.co.uk/diet/low-carb-diabetes-diet.html>
    25. Diabetes.co.uk. Polycystic Ovary Syndrome (PCOS). Date Accessed: 29/04/22. Available from: https://www.diabetes.co.uk/conditions/polycystic-ovary-syndrome.html
    26. Westman, E., Yancy, W., Mavropoulos, J., Marquart, M. and McDuffie, J. The effect of a low-carbohydrate, ketogenic diet versus a low-glycemic index diet on glycemic control in type 2 diabetes mellitus. 2008;

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