Being in ketosis and a calorie deficit but not losing weight is one of the most frustrating experiences for anyone following a ketogenic diet. Despite doing everything seemingly right, the scales can stubbornly refuse to move — and the reasons are rarely straightforward. Human metabolism is far more complex than a simple calories-in-versus-calories-out equation. From hidden carbohydrates and inaccurate calorie tracking to underlying medical conditions, hormonal imbalances, and lifestyle factors such as poor sleep and chronic stress, numerous variables can stall progress. This article explores the most common causes and offers evidence-based, UK-relevant guidance to help you understand and address your plateau.

Why You May Not Lose Weight Despite Ketosis and a Calorie Deficit

It can be deeply frustrating to find yourself in ketosis and maintaining a calorie deficit, yet the scales refuse to budge. Understanding why this happens requires looking beyond the simple equation of 'calories in versus calories out', because human metabolism is considerably more complex than that formula suggests.

Firstly, it is important to clarify what weight loss actually means physiologically. The body stores energy in multiple forms — fat, glycogen, and water — and changes in any of these compartments will affect your weight. When you first begin a ketogenic diet, the dramatic reduction in carbohydrate intake causes the body to deplete its glycogen stores, releasing a significant amount of water in the process. This initial rapid weight loss is largely water, not fat. Once glycogen stores are depleted, the body transitions to burning fat for fuel, but this fat-loss phase is typically slower and more gradual.

Short-term fluctuations in weight are also common and can be influenced by factors unrelated to fat loss, including changes in hydration, sodium intake, bowel habit, and — in women — the menstrual cycle. These fluctuations can mask genuine fat loss and make it difficult to interpret day-to-day changes on the scales.

Weight is not the same as body composition. You may be losing body fat whilst simultaneously gaining lean muscle mass — particularly if you are exercising regularly — resulting in little to no change on the scales. This is sometimes referred to as 'body recomposition' and is a positive physiological outcome, even if it feels discouraging. Measurements such as waist circumference (using NICE- and WHO-recommended cut-offs), body fat percentage, or how clothing fits may be more informative indicators of progress than weight alone.

Finally, the body has sophisticated adaptive mechanisms that resist prolonged caloric restriction. Over time, your basal metabolic rate (BMR) — the number of calories your body burns at rest — can decrease in response to sustained energy restriction, a process known as metabolic adaptation or adaptive thermogenesis. Research by Hall and colleagues, and by Rosenbaum and Leibel, has demonstrated that this adaptation varies considerably between individuals. This means that a calorie deficit that once produced weight loss may no longer be sufficient to do so, and periodic reassessment of your approach is advisable. NICE obesity guidance (NG7 and CG189) emphasises that weight management is a long-term process requiring ongoing support and review.

Common Reasons Weight Loss Stalls on a Ketogenic Diet

A weight loss plateau on a ketogenic diet is more common than many people realise, and there are several well-recognised dietary and behavioural reasons why progress may stall even when you believe you are doing everything correctly.

Hidden carbohydrates are one of the most frequent culprits. Many processed foods, sauces, condiments, and some dairy products contain small amounts of carbohydrate that can accumulate throughout the day. In the UK, nutrition labels list 'carbohydrate' as a figure that already excludes dietary fibre (fibre is listed separately), so the carbohydrate figure shown is the relevant one to monitor — there is no need to calculate 'net carbs' as described on some US-based resources. Consuming more than approximately 20–50 grams of carbohydrate daily — the range commonly cited in ketogenic diet research as the threshold for maintaining ketosis in most people, though individual tolerance varies — can disrupt ketone production without you realising it. Reading food labels carefully, using the per-100 g column for comparisons, and being aware that some products marketed as 'keto-friendly' may still contain significant carbohydrate is essential. It is also worth noting that polyols (sugar alcohols) used in low-carbohydrate products contribute varying amounts of energy and may affect ketosis differently between individuals.

Calorie-dense keto foods present another challenge. Foods commonly consumed on a ketogenic diet — such as nuts, cheese, avocado, cream, and oils — are highly calorific. It is surprisingly easy to underestimate portion sizes and inadvertently consume far more calories than intended. For example:

• A 30 g portion of almonds contains approximately 170 kcal

• Two tablespoons of olive oil contribute around 240 kcal

• A 50 g serving of cheddar cheese provides roughly 200 kcal

These calories add up quickly and can erode a calorie deficit without obvious overeating.

Another consideration is protein intake. On a ketogenic diet, very high protein intake may contribute to glucose production via gluconeogenesis — a process by which the liver produces glucose from amino acids — though this process is largely demand-driven and its practical impact on ketosis varies between individuals. Moderate protein intake is generally recommended to support muscle preservation whilst maintaining ketosis; research suggests a range of approximately 1.2–1.7 grams per kilogram of reference (ideal) body weight per day, though individual needs differ. People with chronic kidney disease (CKD) or other renal conditions should seek specific dietary advice from their GP or a registered dietitian before increasing protein intake.

Lastly, frequent snacking, even on keto-compliant foods, may make it harder to maintain the low insulin environment that supports fat mobilisation, and can also make accurate calorie tracking more difficult. Consolidating eating into defined meals is a practical strategy that some people find helpful, though the evidence for this as an independent mechanism is limited.

Medical Conditions That Can Affect Weight Loss Progress

When dietary and lifestyle factors have been carefully addressed and weight loss still fails to occur, it is worth considering whether an underlying medical condition may be contributing. Several health conditions are known to impair metabolism, promote fat storage, or interfere with the hormonal signals that regulate body weight.

Hypothyroidism is one of the most commonly implicated conditions. The thyroid gland produces hormones — primarily thyroxine (T4) and triiodothyronine (T3) — that regulate metabolic rate throughout the body. When thyroid function is underactive, metabolism slows significantly, making weight loss difficult even with dietary restriction. Symptoms may include fatigue, cold intolerance, constipation, and dry skin. Diagnosis requires blood tests measuring thyroid-stimulating hormone (TSH) and free T4; thyroid peroxidase (TPO) antibodies may also be checked where autoimmune thyroid disease is suspected. NICE guideline NG145 (Thyroid disease: assessment and management) advises that treatment with levothyroxine should be considered when TSH is persistently at or above 10 mIU/L, or may be offered as a trial in symptomatic adults under 65 with TSH between 4 and 10 mIU/L. If you are concerned about your thyroid function, speak to your GP, who can arrange appropriate testing. Further information is available on the NHS website.

Not sure if this is normal? Chat with one of our pharmacists →

Polycystic ovary syndrome (PCOS) is another condition that frequently impairs weight loss, particularly in women of reproductive age. PCOS is associated with insulin resistance, elevated androgen levels, and disrupted hormonal signalling, all of which can promote fat storage — particularly around the abdomen — and make calorie deficits less effective. If you suspect PCOS, your GP can discuss diagnosis (based on the Rotterdam criteria) and management options. The NHS PCOS information page provides a helpful starting point.

Insulin resistance and type 2 diabetes can similarly blunt the body's ability to mobilise stored fat, even in a state of caloric restriction. Elevated circulating insulin levels actively inhibit lipolysis (the breakdown of fat for energy).

⚠️ Important safety information for people with diabetes: Ketogenic diets significantly restrict carbohydrate intake and can alter insulin and medication requirements. People with type 1 diabetes, or those taking SGLT2 inhibitors (such as dapagliflozin, empagliflozin, or canagliflozin), face an increased risk of diabetic ketoacidosis (DKA) — including euglycaemic DKA, which can occur even when blood glucose appears normal. The MHRA has issued Drug Safety Updates on this risk. Anyone with diabetes, or taking glucose-lowering medicines, must consult their GP or diabetes team before starting a ketogenic diet. Do not adjust or stop diabetes medications without medical supervision.

Other conditions worth discussing with your GP include:

• Cushing's syndrome — caused by excess cortisol, and characterised by central weight gain, easy bruising, purple stretch marks (striae), and proximal muscle weakness. If these features are present, prompt GP assessment and possible referral to endocrinology is recommended (see NICE CKS: Cushing's syndrome)

• Depression and anxiety — which can affect appetite regulation, sleep, and motivation

• Certain medicines, including corticosteroids, some antidepressants, antipsychotics, and beta-blockers, which are associated with weight gain as listed in their Summary of Product Characteristics (SmPC) and the British National Formulary (BNF). Do not stop any prescribed medicine without first speaking to your GP or pharmacist. If you believe a medicine may be contributing to weight gain, discuss this with your prescriber, who can advise on alternatives where appropriate.

If you suspect a medical cause for your weight loss difficulties, consult your GP for appropriate investigation and guidance. Suspected side effects of medicines can be reported to the MHRA via the Yellow Card scheme (yellowcard.mhra.gov.uk).

Experiencing these side effects? Our pharmacists can help you navigate them →

Ketogenic diets are generally not recommended during pregnancy or breastfeeding, or for people with significant renal or hepatic disease. If any of these apply to you, please seek advice from your GP or a registered dietitian before making major dietary changes.

How to Accurately Track Calories and Ketosis Levels

Accurate self-monitoring is a cornerstone of successful weight management, yet research consistently shows that people — even those who are highly motivated — tend to underestimate their calorie intake by a significant margin. Studies using doubly labelled water and other objective methods (including work by Schoeller and colleagues, and Archer and colleagues) suggest that self-reported calorie consumption can be underestimated by 20–50% or more, which can entirely negate a perceived calorie deficit. The degree of underestimation varies between individuals and methods.

Tracking calories accurately requires more than rough estimates. The following practices can substantially improve accuracy:

• Weigh food using digital kitchen scales rather than relying on volume measurements such as cups or tablespoons, which are imprecise

• Log everything consumed, including cooking oils, drinks, condiments, and small snacks

• Use a reputable food database to look up nutritional values; the UK reference standard is the CoFID (Composition of Foods Integrated Dataset), published by the Office for Health Improvements and Disparities (OHID), based on McCance and Widdowson's The Composition of Foods. Food tracking applications can be a useful practical tool, but the accuracy of their databases varies; cross-checking key foods against CoFID is advisable

• Account for restaurant and takeaway meals, which often contain significantly more calories than home-cooked equivalents

1. Regarding monitoring ketosis, there are three main methods available:
2. Urine ketone strips — inexpensive and widely available, but measure acetoacetate and become less reliable over time as the body adapts to ketosis and excretes fewer ketones in urine. People with diabetes should not rely on urine strips to assess DKA risk; blood ketone testing is preferred in that context (see Diabetes UK guidance on ketone testing)
3. Blood ketone meters — considered the most accurate method for routine monitoring, measuring beta-hydroxybutyrate (BHB) directly; a BHB level of 0.5–3.0 mmol/L is widely cited in research as indicating nutritional ketosis, though this is a research and industry convention rather than an NHS or NICE clinical standard
4. Breath ketone analysers — measure acetone in exhaled breath and offer a non-invasive, reusable option, though they are generally less precise than blood testing

It is worth noting that being in ketosis does not automatically guarantee a calorie deficit, and vice versa. Both conditions must be present and sustained for consistent fat loss to occur. Ketone testing is optional for weight management purposes and is not required to follow a ketogenic diet safely. If you have concerns about disordered eating or find that monitoring is causing significant anxiety, please speak to your GP, who can signpost appropriate support.

Lifestyle Factors That May Be Slowing Your Progress

Beyond diet and medical considerations, several lifestyle factors can significantly influence weight loss outcomes, even when nutritional targets appear to be met. These factors are often overlooked but are supported by a growing body of clinical evidence.

Sleep quality and duration have a profound effect on metabolic health and weight regulation. Poor sleep is associated with elevated levels of the hunger hormone ghrelin and reduced levels of leptin, the satiety hormone, leading to increased appetite and cravings — particularly for high-calorie foods — that make it harder to maintain a calorie deficit. The NHS advises that most adults need between six and nine hours of sleep per night, though individual needs vary. Prioritising consistent sleep routines and good sleep hygiene is a practical and evidence-supported component of weight management.

Chronic stress is another significant barrier to weight loss. Prolonged psychological stress elevates cortisol, a glucocorticoid hormone that promotes fat storage — particularly visceral (abdominal) fat — and can stimulate appetite. Cortisol also raises blood glucose levels, which may suppress ketone production. Stress management strategies such as mindfulness, regular physical activity, and adequate rest are therefore relevant components of any weight management plan.

Physical activity plays an important role in preserving lean muscle mass during caloric restriction, supporting metabolic rate, and improving insulin sensitivity. The UK Chief Medical Officers' Physical Activity Guidelines recommend that adults aim for at least 150 minutes of moderate-intensity activity, or 75 minutes of vigorous-intensity activity, per week, plus muscle-strengthening activities on at least two days per week. Both resistance training and aerobic exercise are beneficial, and NICE guidance on weight management highlights physical activity as an integral component of a comprehensive approach.

Alcohol consumption is frequently underestimated as a factor. Alcohol contains 7 kcal per gram — more than carbohydrates or protein — and many alcoholic drinks also contain residual sugars that can disrupt ketosis. The UK low-risk drinking guideline advises consuming no more than 14 units of alcohol per week, spread across three or more days, with at least two alcohol-free days each week. Even moderate alcohol intake can stall progress and should be accounted for honestly within daily calorie tracking.

Finally, a ketogenic diet is not suitable for everyone. It is generally not recommended during pregnancy or breastfeeding, for people with significant renal or hepatic disease, or for those with a history of disordered eating. If weight loss remains elusive despite addressing all of the above, or if you have any of these considerations, a referral to a registered dietitian or a consultation with your GP for further assessment is a sensible and recommended next step.

Frequently Asked Questions