Could a low carbohydrate diet help me lose weight?

You may feel as though you have tried everything. Calorie counting. Slimming clubs. Eating well. Moving more. Yet the scales still refuse to shift. When that happens, it makes complete sense to look for a more decisive option.

Many people reach a point where their body no longer responds as it once did. Energy feels stretched thin. At that stage, low-carbohydrate diets often feel like a logical next step.

From Atkins to keto and everything in between, ‘low-carb’ approaches have existed for decades. Before you cut out whole food groups, it helps to understand what these diets involve, how weight loss happens on them, and what that early drop on the scales really means.

What does a low-carbohydrate diet look like?

One of the biggest challenges with low-carb diets is that there is no single agreed definition of what “low-carb” actually means. In research, the amount of carbohydrate allowed can vary widely, which partly explains why results and experiences are so mixed [1]. Some approaches reduce carbohydrates slightly, while others remove them almost entirely [2].

What they usually have in common is:

• Cutting back on foods such as bread, rice, pasta, potatoes, fruit and some vegetables
• Increasing protein and fat, such as:
  • Meat, fish, eggs and cheese
  • Full-fat dairy products
  • Nuts, seeds, oils and butter [3]

Not all carbohydrates affect the body in the same way. A biscuit and a sweet potato both count as carbohydrates, but they do very different things nutritionally. Wholegrains, fruit and vegetables provide fibre, vitamins and minerals, and reducing these foods can lower overall dietary quality [4,5].

How do low-carb diets lead to weight loss?

Carbohydrate is the body’s main fuel source, particularly for the brain. When carbohydrate intake drops sharply, the body first uses up its stored glucose (glycogen) from the liver and muscles. Because glycogen is stored with water, the initial drop on the scales is largely water loss rather than body fat [6].

Once these stores are depleted, the body relies more heavily on fat for energy [7]. In very low-carbohydrate diets, this can lead to ketosis (where fat is converted into ketones for fuel) which is where the ‘keto diet’ gets its name [8].

This explains why people often see a quick change in the first week or two. That early drop can feel very motivating, especially when weight has previously felt stubborn, but this early change does not reflect true fat loss yet [7].

After this early phase, the body returns to its usual weight-regulation systems. From that point onwards, further change depends on how well the overall pattern of eating supports metabolism, muscle mass, appetite, sleep and daily demands, not simply on whether carbohydrates are present or not. This is often when progress slows or stalls.

Most weight-loss approaches work because they reduce overall energy intake, not because carbohydrates themselves are uniquely responsible for weight gain [1].

Are there downsides to cutting carbohydrates?

Any highly restrictive way of eating has trade-offs. In the early weeks, people commonly experience:

• Fatigue or “brain fog”
• Headaches
• Irritability
• Constipation
• Strong hunger or cravings [8]

Long-term carbohydrate restriction often lowers fibre intake. Low fibre can disrupt digestion, cholesterol levels and blood sugar stability. Prolonged restriction can also reduce nutrients that support heart and bone health [9].

Very low-carbohydrate diets can also cause further effects such as bad breath, muscle weakness and headaches [10].

Despite their popularity, researchers still have limited evidence on the long-term safety of low-carb diets across the general population. Concerns include nutrient deficiencies, fatigue, disordered eating patterns and reduced physical performance [1].

Low-carb and ketogenic approaches do have a place in specific medical situations. These include epilepsy and selected diabetes care under healthcare professional supervision. But these are therapeutic tools, not general weight-management strategies [6].

Are low-carb diets a good long-term solution?

Low-carbohydrate diets rarely offer the most reliable long-term solution for sustainable weight change.

If you’re drawn to one because weight feels harder than it used to, you’re frustrated with slow progress or you genuinely feel you’ve “tried everything”, it may be worth asking whether your body needs more restriction, or a more suitable approach for you.

It’s important to recognise that weight regulation is influenced by many factors:

• Changes in metabolism and muscle mass across life stages
• Sleep quality
• Stress management
• Appetite regulation
• Hormonal shifts

Simply removing a food group doesn’t address these drivers, and can sometimes make them harder to manage.

A more realistic way forward

Rather than focusing on whether carbohydrates should be removed, a more helpful consideration could be, looking at what pattern of eating supports your weight, your energy and your lifestyle right now.

For many people, this looks like:

• Prioritising enough protein at meals
• Including carbohydrates in appropriate portions rather than cutting them out
• Choosing higher-fibre, minimally processed carbohydrate sources most of the time
• Supporting muscle through nutrition and everyday movement, which helps maintain metabolism and strength as the body changes
• Eating in a way that stabilises hunger and energy across the day

This approach usually leads to slower weight change, but it is far more likely to be maintained, and far less likely to lead to repeated cycles of loss and regain [11,12].

Bottom line

Low-carbohydrate diets can produce rapid initial weight loss, largely through water and glycogen loss. Once this early phase passes, further progress depends on how well the overall way of eating supports your body, not simply on carbohydrate removal.

For many people, low-carb diets are difficult to sustain and don’t address why weight becomes harder to manage over time [13].

If you feel stuck with your weight despite genuine effort, it doesn’t mean it’s impossible, it means your body’s needs may have changed. Working with a dietitian can help you understand what’s happening and find a way forward that supports both your health and your goals without extreme restriction.

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References

1. Chacón, V., Cara, K. C., Chung, M., & Wallace, T. C. (2025). Defining “low-carb” in the scientific literature: A scoping review of clinical studies. Critical Reviews in Food Science and Nutrition, 65(10), 1792–1801. https://doi.org/10.1080/10408398.2023.2300705
2. Oh R, Gilani B, Uppaluri KR. Low Carbohydrate Diet. 2023 Jan 10. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan–.
3. Mayo Clinic, 2022. Low-carb diet: Can it help you lose weight? Accessed 30th March 2022. Online, available at: https://www.mayoclinic.org/healthy-lifestyle/weight-loss/in-depth/low-carb-diet/art-20045831
4. Holesh JE, Aslam S, Martin A. Physiology, Carbohydrates. 2022 Jul 25. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan–.
5. Ludwig DS, Hu FB, Tappy L, Brand-Miller J. Dietary carbohydrates: role of quality and quantity in chronic disease. BMJ. 2018 Jun 13;361:k2340
6. Hall KD, Heymsfield SB, Kemnitz JW, Klein S, Schoeller DA, Speakman JR. Energy balance and its components: implications for body weight regulation. Am J Clin Nutr. 2012 Apr;95(4):989-94
7. Sukkar, S.G., & Muscaritoli, M. (2021). A Clinical Perspective of Low Carbohydrate Ketogenic Diets: A Narrative Review. Frontiers in Nutrition, 8.
8. Dyńka, D., Rodzeń, Ł., Rodzeń, M., Pacholak-Klimas, A., Ede, G., Sethi, S., Łojko, D., Bartoń, K., Berry, K., Deptuła, A., Grzywacz, Ż., Martin, P., Unwin, J., & Unwin, D. (2025). Ketogenic Diets for Body Weight Loss: A Comparison with Other Diets. Nutrients, 17(6), 965. https://doi.org/10.3390/nu17060965
9. Barber TM, Hanson P, Kabisch S, Pfeiffer AFH, Weickert MO. The Low-Carbohydrate Diet: Short-Term Metabolic Efficacy Versus Longer-Term Limitations. Nutrients. 2021 Apr 3;13(4):1187.
10. Diabetes UK, 2019. Low Carb Diet Side Effects. Accessed 29th March 2023. Online, available at: https://www.diabetes.co.uk/diet/low-carb-diet-side-effects.html
11. Cleveland Clinic, 2022. Ketosis. Accessed 30th March 2023. Online, available at: https://my.clevelandclinic.org/health/articles/24003-ketosis
12. Winwood-Smith HS, Franklin CE, White CR. Low-carbohydrate diet induces metabolic depression: a possible mechanism to conserve glycogen. Am J Physiol Regul Integr Comp Physiol. 2017 Oct 1;313(4):R347-R356.
13. Chawla S, Tessarolo Silva F, Amaral Medeiros S, Mekary RA, Radenkovic D. The Effect of Low-Fat and Low-Carbohydrate Diets on Weight Loss and Lipid Levels: A Systematic Review and Meta-Analysis. Nutrients. 2020 Dec 9;12(12):3774.