Low-carb or keto: the short answer
Eating low-carb means taking in fewer carbohydrates than average each day, usually somewhere between 50 and 130 grams. Keto is a stricter variant that keeps you under 20 to 30 grams of carbohydrate a day. That threshold isn't arbitrary: it's only below this level that your body switches to a genuinely different fuel source.
The two terms are often used interchangeably, but they describe fundamentally different metabolic states. On a low-carb diet, you typically remain on glucose as your primary fuel. On keto, you're deliberately pushing your body into ketosis. What that actually involves, and which approach is safer and more sustainable for you, is what we'll unpack below.
What is ketosis, and when does it kick in
Ketosis is a physiological state in which your liver produces ketone bodies from fat reserves. This happens when glycogen stores in the liver and muscles run low and there isn't enough glucose available as fuel. The brain, which normally runs on glucose, then switches largely to beta-hydroxybutyrate, one of the three ketone bodies.
The threshold varies from person to person, but most research uses 20 to 30 grams of net carbohydrate per day as the point at which nutritional ketosis reliably sets in. Net carbs are total carbohydrates minus fibre, since fibre isn't converted into glucose.
Ketosis is not the same as diabetic ketoacidosis. The latter is a life-threatening condition that occurs almost exclusively in people with type 1 diabetes, with ketone levels ten to twenty times higher. Nutritional ketosis in healthy people sits between 0.5 and 3.0 mmol/L of blood ketones. Diabetic ketoacidosis starts above 10 mmol/L.
Whether ketosis offers long-term benefits beyond epilepsy treatment is still the subject of ongoing research. The Dutch Nutrition Centre (Voedingscentrum) currently doesn't recommend a strict ketogenic diet as standard nutritional advice for the general population, partly due to the lack of long-term data.
Comparison: low-carb versus keto
| Feature | Low-carb | Ketogenic (keto) |
|---|---|---|
| Carbohydrates per day | 50 to 130 grams | Under 20 to 30 grams |
| Protein per day | 1.6 to 2.2 grams per kg body weight | 1.2 to 1.7 grams per kg body weight |
| Fat as percentage of energy | 30 to 45 percent | 60 to 80 percent |
| Metabolic state | Glucose remains the primary fuel | Ketosis: ketone bodies as primary fuel |
| Measurable with a blood meter | No | Yes, via blood ketones (0.5 to 3.0 mmol/L) |
| Flexibility in food choice | Reasonable: vegetables, fruit, wholegrains | Limited: virtually no fruit, grains or pulses |
| Adjustment period side effects | Mild (1 to 3 days) | Moderate to severe (3 to 10 days, keto flu) |
| Suitable for long-term use | Yes, well supported by evidence | Limited evidence beyond 12 months |
| Medical supervision advised | For specific conditions | Always recommended |
Pros and cons of eating low-carb
Pros
- Steadier blood sugar: Fewer carbohydrates mean smaller glucose spikes after meals. This matters particularly for insulin resistance and prediabetes.
- Higher protein intake supports muscle preservation: On a low-carb diet with sufficient protein (1.6 grams per kg body weight), muscle loss during weight loss is demonstrably lower. This is backed by a meta-analysis published in Nutrients (2016).
- Practical to sustain: Fruit, pulses and wholegrain products can still feature in a low-carb approach, which helps keep nutritional value and enjoyment on track.
- Proven weight loss: Studies consistently show average weight loss of 3 to 6 kilograms over the first 12 weeks, comparable to other calorie-restricted diets.
Cons
- Less fibre if you restrict vegetables and fruit, which can affect gut health.
- Requires more planning than a standard eating pattern.
- Not automatically suited to intensive endurance training without adjusting the timing of carbs around workouts.
Pros and cons of keto
Pros
- Strong clinical application in refractory epilepsy: Keto is the most well-established non-drug treatment for children with hard-to-treat epilepsy. The British Dietetic Association (BDA) recognises it as a clinical protocol.
- Rapid initial weight loss: In the first two weeks, people on keto lose 1.5 to 3 kilograms more on average than on a standard low-calorie diet. This is largely water loss caused by glycogen depletion (every gram of glycogen holds roughly 3 grams of water).
- Appetite suppression: Ketone bodies have an appetite-suppressing effect, possibly by influencing ghrelin levels.
Cons
- Extremely restrictive: a single meal with an extra 30 grams of carbohydrate is enough to knock you out of ketosis.
- High saturated fat intake, if poorly implemented, can raise LDL cholesterol.
- Limited long-term data: most trials run for 12 to 24 weeks. Data covering 2 years or more are scarce.
- Not suitable without medical supervision for kidney problems, liver conditions or type 1 diabetes.
- Difficult to maintain socially and practically.
Keto side effects: the keto flu
In the first three to ten days of a strict ketogenic diet, most beginners experience a cluster of symptoms known as the keto flu. This is a physiological adjustment response, not an infection.
Common symptoms
- Fatigue and reduced concentration
- Headaches (reported by 60 to 70 percent of beginners in observational data)
- Nausea
- Irritability
- Muscle cramps, particularly at night
- Constipation due to reduced fibre intake
Cause
As glycogen stores empty, the kidneys excrete sodium faster, taking potassium and magnesium along with it. This electrolyte loss explains most of the symptoms. Increasing your intake of salt, magnesium (300 to 400 mg per day) and potassium demonstrably reduces symptoms, though it doesn't eliminate them entirely.
Duration
With consistent keto eating, symptoms disappear for most people within seven to ten days. For some, reduced sporting performance can linger for three to four weeks, the time needed for full metabolic keto-adaptation.
Sustainability: what the research says
Sustainability is the weak link in most diet studies. In randomised trials, dropout rates for keto tend to run higher than for moderate low-carb diets. A review in The Lancet Diabetes and Endocrinology found that after 12 months, the difference in weight loss between keto and other diets was no longer statistically significant, largely because most keto participants couldn't maintain the restrictions.
Low-carb eating without a strict keto threshold offers more room to manoeuvre. A portion of berries (15 grams of carbohydrate), a small serving of lentils, or a slice of wholemeal bread all fit within a low-carb plan of 100 grams a day. That's what makes the practical difference: at a birthday, on holiday, in a restaurant. Small deviations don't derail a low-carb plan, but they will break a gram-precise keto protocol.
Research into behaviour change (including from the BDA) highlights that a diet followed 80 percent of the time works better than one followed with 100 percent precision but abandoned after six weeks. For most people, low-carb is therefore more effective in the long run, not because it's metabolically superior, but because it's achievable.
The approach Bioteïne takes starts from this exact principle. If you'd like to understand what a structured, high-protein, low-carb plan looks like, the high-protein diet guide offers a clear starting point.
What Bioteïne recommends: balanced low-carb
Bioteïne was built as a protein-first nutrition range, not a keto brand. That's a deliberate choice, based on three practical considerations.
1. Protein intake comes first
On a strict ketogenic diet, protein is kept moderate, because too much protein can be partly converted into glucose via gluconeogenesis, which disrupts ketosis. That means keto and a high protein intake (1.8 to 2.2 grams per kg) don't sit comfortably together. For preserving muscle while losing weight, however, a higher protein intake is demonstrably more effective. Bioteïne opts for the protein advantage.
2. The 4-phase approach
Bioteïne's 4-phase system uses low-carb eating that's flexible enough to sustain long-term. Each phase builds on the last, allowing the body to adapt gradually without the extreme transition symptoms of keto. The first phase brings carbohydrates down to 60 to 80 grams a day, a level that stabilises blood sugar without triggering the keto flu.
3. Products designed for compliance
Bioteïne's protein shakes, high-protein meals and protein bars are formulated with 20 to 30 grams of protein per serving and a limited amount of carbohydrate, without the fat density of a typical keto product. That makes them workable within a low-carb diet of 80 to 130 grams a day, but equally within a stricter 50-gram approach if that's medically advised.
Not sure which approach suits your situation? Take the phase test. Based on your current eating pattern, activity level and goal, you'll get a concrete starting point without having to work out the grams of carbohydrate or protein you need each day yourself.
The starter pack also offers a practical way in: all products for the first four weeks are put together based on the 4-phase plan, including a daily eating schedule.
For additional quick options without much carbohydrate, the protein snacks and protein biscuits make a good swap for standard snacks, which typically contain 25 to 40 grams of carbohydrate per portion.
Frequently asked questions
What's the difference between low-carb and keto?
Eating low-carb means taking in 50 to 130 grams of carbohydrate a day. Keto is stricter: under 20 to 30 grams a day, so the body switches to ketone bodies as fuel. This is called ketosis. The difference lies in the metabolic state, not just the quantity.
Is keto dangerous?
For healthy adults with no underlying conditions, keto isn't dangerous in the short term, but side effects are common. For those with kidney problems, liver conditions or type 1 diabetes, medical supervision is essential. Long-term data beyond 24 months are largely lacking, which justifies a degree of caution.
What is the keto flu, and how long does it last?
The keto flu is an adjustment response occurring in the first three to ten days of keto: fatigue, headaches, muscle cramps and nausea caused by electrolyte loss. Symptoms disappear for most people within seven to ten days. Extra salt, magnesium and potassium reduce the severity.
How many carbohydrates can you eat on a low-carb diet?
A common definition of low-carb is 50 to 130 grams of net carbohydrate per day. Net means total carbohydrates minus fibre. The exact threshold depends on your activity level, body weight and health goal. For intensive athletes, an upper limit of 130 grams can still count as low-carb.
Do you lose weight faster on keto than on low-carb?
In the first two weeks, keto users show 1.5 to 3 kilograms more weight loss on average. This is largely water loss from glycogen depletion. After 12 months, the difference in fat mass loss between keto and moderate low-carb diets is no longer statistically significant, according to several randomised trials.
Can I combine keto with a high protein intake?
That's tricky. A high protein intake (above 1.8 grams per kg body weight) can disrupt ketosis via gluconeogenesis. Keto requires moderate protein and high fat intake. If preserving muscle is your priority, a low-carb plan with a higher protein intake is a better fit than strict keto.
Is low-carb or keto better for sustainability?
Low-carb eating without a strict keto threshold is easier for most people to sustain. A review in The Lancet Diabetes and Endocrinology showed higher dropout rates on keto, with weight benefits levelling out after 12 months. Flexibility in food choice is the deciding factor over the long term.
How do I know which approach suits me?
That depends on your starting weight, activity level, medical situation and how your body responds to carbohydrate restriction. Bioteïne's phase test gives you personalised starting advice based on a short questionnaire, including target figures for protein and carbohydrate per day.