Protein Rich Foods for Intermittent Fasting

Protein rich foods for intermittent fasting are a cornerstone of any well-structured IF plan, helping to preserve muscle mass, support satiety and maintain metabolic health within a compressed eating window. Whether you follow a 16:8 schedule or a 5:2 approach, the quality and quantity of protein you consume during your eating window can significantly influence how comfortable and effective your fasting experience is. This article covers the best protein sources, how much to aim for, practical meal ideas and who should seek professional advice before starting.

Why does protein matter so much when you're intermittent fasting?

Protein is essential during intermittent fasting because it preserves lean muscle mass, supports satiety through appetite-suppressing gut hormones, and contributes to energy balance without excess calories.

Protein is an important macronutrient to prioritise during intermittent fasting, alongside adequate carbohydrates, fats and fibre, because it helps preserve lean muscle mass during the periods when you are not eating. When the body is in a fasted state, it draws on stored energy, and without adequate dietary protein, it can begin to break down muscle tissue for fuel, a process known as catabolism.^[9] Ensuring sufficient protein intake during your eating window helps counteract this risk.

Protein also plays a central role in satiety. Evidence from dietary research suggests it stimulates the release of appetite-suppressing gut hormones such as peptide YY and GLP-1, and may reduce levels of ghrelin, the hormone associated with hunger.^[4][5] This hormonal response can make the fasting periods feel more manageable, particularly in the early weeks of adopting an intermittent fasting (IF) plan.

From a metabolic standpoint, protein has a higher thermic effect than carbohydrates or fats, meaning the body uses more energy to digest and absorb it.^[6] This difference is modest in absolute terms and should not be relied upon alone for weight management, but it does mean that protein contributes to overall energy balance without requiring you to eat more calories. For anyone using IF as part of a broader approach to weight management or metabolic health, protein is a foundational element of the strategy, though a balanced dietary pattern overall remains important.

Which protein rich foods are best to eat during your eating window?

The best protein rich foods include eggs, chicken breast, oily fish, Greek yoghurt and legumes, chosen for their high protein density, essential amino acid profiles and additional nutrients such as fibre and omega-3s.

The best protein-rich foods to eat during an intermittent fasting eating window are those that combine high protein density with good digestibility and, ideally, a range of essential amino acids. Both animal and plant-based sources can meet these criteria, and variety across the week is generally advisable.

Animal-based sources worth including regularly:

• Eggs: A complete protein source containing all nine essential amino acids, versatile and quick to prepare.

• Chicken breast and turkey: Lean, high in protein and low in saturated fat.

• Oily fish (salmon, mackerel, sardines): Provide protein alongside omega-3 fatty acids, which support cardiovascular health. NHS guidance recommends two portions of fish per week, of which one should be oily.^[1]

• Greek yoghurt and cottage cheese: Dairy options that are high in protein and also contribute calcium.

• Lean red meat (beef, lamb): Rich in protein, iron and B vitamins. NHS guidance recommends keeping red and processed meat intake to no more than approximately 70 g per day (cooked weight) and choosing lean, unprocessed cuts where possible.^[2] Processed meats such as bacon, sausages and salami are best limited.

Plant-based sources that offer strong protein content:

• Legumes (lentils, chickpeas, black beans): Also high in fibre, which further supports satiety.

• Tofu and tempeh: Soya-based complete proteins suitable for vegetarian and vegan diets.

• Edamame: A convenient, nutrient-dense snack.

• Quinoa: One of the few plant foods that provides all essential amino acids.^[10]

When planning meals for your eating window, combining plant proteins (for example, rice and lentils) can improve the overall amino acid profile.^[12] Choosing minimally processed sources over protein bars or shakes where possible is generally preferable, as whole foods also deliver micronutrients and fibre. Protein estimates in this article are approximations; values vary by brand and preparation, so checking UK nutrition labels is advisable.

How much protein should you aim for each day on an IF plan?

Most adults on an IF plan should target 1.2 to 2.0 g of protein per kilogram of body weight daily, distributed across all meals within the eating window rather than consumed in one sitting.

Most adults following an intermittent fasting plan should aim for approximately 1.2 to 2.0 grams of protein per kilogram of body weight per day, with the higher end of this range being more appropriate for those who are physically active, older, or seeking to preserve muscle mass. The UK Reference Nutrient Intake (RNI) for protein, established by the Scientific Advisory Committee on Nutrition (SACN) and its predecessor COMA, is 0.75 g per kilogram of body weight per day for sedentary adults. This represents a minimum to meet population needs rather than an optimal target for those using IF alongside exercise or weight management goals.

Because intermittent fasting compresses eating into a shorter window, typically 8 hours in a 16:8 protocol or two meals in a 5:2 approach, it is important to distribute protein intake across all meals within that window rather than concentrating it in a single sitting. Research suggests that spreading protein across two or three meals supports muscle protein synthesis more effectively than consuming a very large amount at once, though the optimal amount per meal varies depending on body mass, age and meal composition.^[8]

For practical reference, a 70 kg moderately active adult aiming for 1.6 g per kilogram would need approximately 112 grams of protein daily. This is achievable across a standard eating window with careful planning. Individual requirements vary based on age, health status and activity level. Anyone with kidney disease or other relevant conditions should seek personalised guidance from a registered dietitian or their GP before significantly increasing protein intake.

Who should seek advice before starting IF or a higher-protein diet? The following groups should speak to their GP or a registered dietitian before beginning intermittent fasting or substantially increasing protein intake: people who are pregnant or breastfeeding; those under 18 years of age; anyone with a current or past history of an eating disorder; people with diabetes who are treated with insulin or sulfonylureas (due to the risk of hypoglycaemia during fasting periods); and those with advanced chronic kidney disease.^[11] This list is not exhaustive, and if you are unsure whether IF is suitable for you, a healthcare professional can provide personalised advice.

Can high protein foods help reduce hunger between fasting periods?

Yes, high protein foods reduce hunger by slowing gastric emptying, stimulating satiety hormones and helping stabilise blood glucose, making fasting periods more comfortable.

High protein foods can meaningfully reduce hunger during fasting periods, and this is one of the most well-supported practical benefits of prioritising protein on an IF plan. Evidence from dietary research, including systematic reviews of higher-protein diets, indicates that protein promotes satiety through several overlapping mechanisms: it slows gastric emptying, is associated with greater release of appetite-suppressing gut hormones, and may help stabilise blood glucose levels, all of which can contribute to a more comfortable fasting experience.

Studies have consistently shown that higher-protein meals lead to greater feelings of fullness compared with meals of equivalent calorie content that are higher in carbohydrates or fat.^[5][7] For someone following a 16:8 fasting schedule, for example, ending the eating window with a protein-rich meal rather than a carbohydrate-heavy one may help reduce the urge to eat during the overnight and morning fasting hours.

It is also worth considering the role of fibre alongside protein. Foods such as lentils, chickpeas and edamame provide both, and this combination tends to produce a more sustained satiety effect than protein alone. Pairing a lean protein source with a fibre-rich vegetable or legume at each meal within the eating window is a practical strategy for managing hunger.

That said, hunger during fasting is also influenced by hydration, sleep quality, stress levels and individual metabolic variation. Drinking adequate water and herbal teas during fasting hours can help distinguish genuine hunger from thirst. If hunger remains difficult to manage despite adequate protein intake, it may be worth reviewing the overall dietary pattern with a healthcare professional or registered dietitian. People with diabetes who take insulin or sulfonylureas should be aware of the additional risk of hypoglycaemia during fasting and should discuss this with their GP or diabetes team before starting an IF plan.

Practical meal ideas to hit your protein targets while fasting

Practical high-protein meals for IF include scrambled eggs with smoked salmon, grilled chicken with roasted vegetables, and lentil dahl with brown rice, providing roughly 25 to 45 g of protein per meal.

Hitting daily protein targets within a compressed eating window is straightforward with a little advance planning, and the meals do not need to be complicated or time-consuming. The following ideas are designed to be practical for common IF schedules such as 16:8 or 18:6. Protein values are estimates based on typical UK portion sizes and will vary by brand and preparation; checking UK nutrition labels is recommended.

First meal (breaking the fast):

• Scrambled eggs (three large eggs) with smoked salmon on wholegrain toast: approximately 35 to 40 g protein.

• Greek yoghurt (full-fat, 200 g) with mixed seeds and berries: approximately 18 to 20 g protein.

• Cottage cheese (150 g) on rye crispbreads with sliced cucumber and cherry tomatoes: approximately 18 to 20 g protein.

Main meal:

• Grilled chicken breast with roasted sweet potato and a large portion of steamed broccoli: approximately 40 to 45 g protein.

• Baked salmon fillet with quinoa and a spinach and edamame salad: approximately 38 to 42 g protein.

• Lentil and chickpea dahl with a portion of brown rice and a side of natural yoghurt: approximately 25 to 30 g protein (suitable for vegetarians).

Snack (if the eating window allows):

• A small handful of edamame (approximately 100 g) or a boiled egg.

• A portion of hummus (approximately 60 g) with vegetable crudités. Note that hummus is moderate rather than high in protein, so it works best as a complement to a protein-rich meal rather than a primary protein source.

Batch cooking proteins such as chicken, lentils or hard-boiled eggs at the start of the week reduces the daily effort considerably. Keeping a simple food diary for the first few weeks can help identify whether protein targets are being met consistently. For those who find it difficult to meet their needs through food alone, an unflavoured whey or pea protein powder added to a smoothie or porridge can bridge the gap without significantly altering the meal's character.

Scientific References

1. Fish and shellfish nutrition.
2. Meat in your diet.
3. Omega-3 – British Dietetic Association.
4. High protein intake stimulates postprandial GLP1 and PYY release.
5. Effect of short- and long-term protein consumption on appetite and appetite-regulating gastrointestinal hormones: a systematic review and meta-analysis of randomized controlled trials. Physiology & Behavior.
6. The role of protein in weight management. Noakes M.
7. A dairy-based, protein-rich breakfast enhances satiety and cognitive concentration before lunch in overweight to obese young females: A randomized controlled crossover study. Journal of Dairy Science.
8. Effect of 3 Different Daily Protein Intakes in a 2-Meal Eating Pattern on Protein Turnover in Middle Age and Older Adults: A Randomized Controlled Trial. The Journal of Nutrition.
9. Molecular Basis and Practical Applications of Training, Nutrition and Recovery for Maximum Gains in Lean Muscle Mass: A Narrative Review for Optimizing Muscular Hypertrophy. Sports Health.
10. Potential of Andean Grains as Substitutes for Animal Proteins in Vegetarian and Vegan Diets: A Nutritional and Functional Analysis. Foods (Basel, Switzerland).
11. Is Time-Restricted Eating Safe in the Treatment of Type 2 Diabetes?—A Review of Intervention Studies. Nutrients.
12. Cereal-Legume Food Matrices as Functional Systems: Processing-Driven Synergies in Nutrition, Bioactive Compounds and Sensory Acceptability. Molecules (Basel, Switzerland).
13. SACN statement on expressing energy, fat and carbohydrate intakes and recommendations.

Frequently Asked Questions