Low-Carb Diet: Benefits and Drawbacks

Is a low-carb diet right for you? A balanced look at the benefits, risks, and scientific evidence behind carbohydrate restriction.

Low-carb diet — what does it mean?

A low-carbohydrate or carb-free diet is one of the most popular weight loss trends. From the Atkins diet to keto and various forms of carb restriction — limiting carbohydrates has been in the spotlight for decades.

But what does science actually say? Is cutting carbs an effective and safe way to lose weight? And who is it suitable for — or not?

In this article, we review the different levels of carb restriction, the research evidence, and practical considerations, especially from the perspective of women's health.

Levels of carbohydrate restriction

Not all low-carb diets are the same. They can be roughly divided into three levels:

- Moderate restriction (100–150 g/day): Reduce sugar and refined carbs while still eating whole grains, fruits, and root vegetables. This aligns with most nutritional guidelines.
- Low-carb (50–100 g/day): Significantly restricted but not in ketosis. Bread, pasta, and rice are eliminated or drastically reduced.
- Ketogenic (under 20–50 g/day): Very strict restriction that forces the body into ketosis — using fat as its primary energy source.

Proven benefits

1. Rapid initial weight loss

A low-carb diet typically produces faster weight loss in the first weeks compared to a low-fat diet. According to research, the low-carb group lost an average of 5.8 kg more over 6 months than the low-fat group (Brehm et al., 2003).

However, it is important to note that much of the initial weight loss is due to fluid loss, not fat burning. As glycogen stores deplete, the body releases the water bound to them.

2. Reduced hunger

Restricting carbs and increasing protein and fat can reduce hunger. This is due to several mechanisms:
- Protein and fat digest more slowly than carbs
- Ketone bodies can reduce appetite
- Stable blood sugar reduces hunger spikes

In studies, those following a low-carb diet reported less hunger than those on a low-fat diet (Gibson et al., 2015).

3. Improved blood lipid profile

A low-carb diet can improve certain blood lipid values, particularly raising HDL cholesterol (good cholesterol) and lowering triglycerides. These changes are associated with reduced heart disease risk (Volek et al., 2009).

4. Improved blood sugar control

Especially for type 2 diabetics or prediabetics, carb restriction can significantly improve blood sugar control and reduce the need for insulin medication.

Proven drawbacks and risks

1. Questionable long-term effectiveness

While a low-carb diet produces faster results in the short term, long-term studies tell a different story. In a two-year follow-up study, the difference in weight loss between low-carb and low-fat diets was practically nonexistent (Foster et al., 2010).

This suggests that what determines weight loss is the calorie deficit, not restricting any single nutrient.

2. Nutrient deficiencies

Strict carb restriction can lead to deficiencies in several important nutrients:
- Fiber: Cutting fruits, whole grains, and root vegetables significantly reduces fiber intake, affecting gut health
- B vitamins: Thiamine and folate in particular may become insufficient
- Magnesium and potassium: Important electrolytes obtained abundantly from fruits and whole grains
- Plant phytochemicals: Protective compounds found in diverse plant-based foods

3. Effects on women's hormonal function

This is an especially important consideration for women. Research suggests that a very low-carb diet can disrupt women's hormonal function:
- Thyroid hormone (T3) production may decrease
- Cortisol levels may rise
- Menstrual cycle may become disrupted
- Fertility may be impaired

For active women in particular, overly strict carb restriction combined with intense training can lead to RED-S syndrome (Relative Energy Deficiency in Sport) (Mountjoy et al., 2018).

4. Social and psychological drawbacks

Strict carb restriction can be socially limiting and psychologically burdensome. When you cannot eat bread, pasta, rice, fruit, or many other common foods, it affects:
- Family meals
- Restaurant visits
- Social situations
- Food-related anxiety

Diets that restrict entire food groups often lead to yo-yo dieting.

5. Deterioration of gut health

Beneficial gut bacteria need fiber for nourishment, which comes primarily from carbohydrate-rich foods. Studies show that a ketogenic diet can reduce gut microbiome diversity (Olson et al., 2018).

Ketosis — what does it mean for your body?

The goal of a ketogenic diet is to achieve ketosis, where the body uses fatty acids and the ketone bodies formed from them as an energy source instead of glucose.

Ketosis is a natural metabolic state that activates during prolonged fasting, for example. It is not the same as ketoacidosis, which is a dangerous condition typically associated with untreated type 1 diabetes.

In the early stages of ketosis, many people experience so-called "keto flu":
- Fatigue and weakness
- Headache
- Irritability
- Difficulty concentrating
- Nausea

These symptoms result from the body adapting to a new energy source and typically last 1–2 weeks.

Who is a low-carb diet suitable for?

Based on research, a low-carb (not ketogenic) diet may be suitable for:
- Type 2 diabetics or prediabetics to support blood sugar control
- People who feel they are carb-sensitive (intense hunger after a carb-heavy meal)
- Those who enjoy protein- and fat-rich foods

It is probably not suitable for:
- Pregnant or breastfeeding women
- Actively training athletes
- Those with a history of eating disorders
- People who find food restrictions psychologically burdensome

A balanced approach to carbohydrates

Rather than completely eliminating carbs, researchers recommend improving carbohydrate quality:

- Choose slow carbs: Whole grains, legumes, root vegetables
- Avoid fast carbs: White sugar, white bread, candy
- Eat carbs together with protein and fiber: This stabilizes blood sugar
- Time your carbs: Consume most carbohydrates around exercise
- Listen to your body: Everyone responds to carbs individually

Summary: weighing the pros and cons

A low-carb diet can be an effective short-term weight loss tool, but its long-term benefits are questionable. For women in particular, very strict carb restriction may cause more harm than good.

The most effective and sustainable approach is to focus on carbohydrate quality, eat enough protein, and create a moderate calorie deficit. This gives you the best results without health risks.

Remember, the best diet is one you can follow permanently — not for a week or a month, but for the rest of your life.

References:
- Brehm, B.J. et al. (2003). A Randomized Trial Comparing a Very Low Carbohydrate Diet and a Calorie-Restricted Low Fat Diet. Journal of Clinical Endocrinology & Metabolism, 88(4), 1617-1623.
- Gibson, A.A. et al. (2015). Do ketogenic diets really suppress appetite? Obesity Reviews, 16(1), 64-76.
- Foster, G.D. et al. (2010). Weight and Metabolic Outcomes After 2 Years on a Low-Carbohydrate Versus Low-Fat Diet. Annals of Internal Medicine, 153(3), 147-157.
- Mountjoy, M. et al. (2018). IOC consensus statement on relative energy deficiency in sport. British Journal of Sports Medicine, 52(11), 687-697.
- Volek, J.S. et al. (2009). Carbohydrate Restriction has a More Favorable Impact on the Metabolic Syndrome than a Low Fat Diet. Lipids, 44(4), 297-309.

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Last updated: March 15, 2025