Understanding the Ketogenic Diet
The ketogenic (keto) diet is a very low carbohydrate, moderate protein, high fat diet that shifts your body into a metabolic state called ketosis. In ketosis, your body becomes remarkably efficient at burning fat for energy instead of relying on carbohydrates.
When you drastically reduce carb intake, your body runs out of its preferred fuel source (glucose). Within a few days, it begins breaking down fat into molecules called ketones, which your brain and body can use for energy. This is the foundation of the keto diet.
Standard Keto Macros
How Ketosis Works
Normally, your body converts carbohydrates into glucose, which is used for immediate energy or stored as glycogen in your liver and muscles. When carbs are restricted:
- Glycogen depletes — Your body uses up stored carbohydrates within 24-48 hours
- Fat breakdown begins — Your liver starts converting fatty acids into ketone bodies
- Ketones fuel your body — Your brain, heart, and muscles adapt to using ketones for energy
- Fat becomes primary fuel — Your body becomes "fat-adapted" and efficiently burns both dietary fat and body fat
The Science of Appetite Suppression on Keto
One of the most notable effects of ketosis is dramatically reduced hunger. Research published in the European Journal of Clinical Nutrition found that ketogenic diets suppress appetite through multiple mechanisms:
Ketones directly suppress appetite — Ketone bodies appear to act on hunger centres in the brain, reducing the drive to eat.
Stable blood sugar — Without carbs spiking and crashing your blood glucose, you don't experience the "hunger crashes" that drive snacking.
Higher satiety from fat and protein — These macronutrients keep you fuller for longer than carbohydrates.
Many people on keto report being able to skip meals easily, having no interest in snacking, and feeling satisfied on fewer total calories without deliberate restriction.
What to Eat on Keto
Keto focuses on whole, unprocessed foods that are naturally low in carbohydrates:
Keto-Friendly Foods
- Meats: Beef, pork, lamb, chicken, turkey, bacon
- Fatty fish: Salmon, mackerel, sardines
- Eggs: Whole eggs, any style
- High-fat dairy: Butter, cream, hard cheeses
- Nuts & seeds: Almonds, walnuts, macadamias
- Healthy oils: Olive oil, coconut oil, avocado oil
- Low-carb veg: Leafy greens, broccoli, cauliflower
- Avocados: High fat, very low carb
Foods to Avoid
- Grains: Bread, pasta, rice, oats, cereals
- Sugar: Sweets, chocolate, fizzy drinks, fruit juice
- Starchy veg: Potatoes, sweet potatoes, carrots
- Most fruits: Bananas, apples, oranges (small berries OK)
- Beans & legumes: Kidney beans, chickpeas, lentils
- Low-fat products: Often high in added sugar
- Sauces: Ketchup, BBQ sauce (check labels)
- Alcohol: Beer, sweet wines, cocktails
Getting into Ketosis: What to Expect
The transition to ketosis takes most people 2-7 days. Here's what typically happens:
Days 1-2: Glycogen Depletion
Your body uses up stored carbohydrates. You may feel normal, slightly tired, or experience increased urination as glycogen releases water.
Days 3-5: "Keto Flu"
Some people experience headaches, fatigue, brain fog, or irritability as the body adapts. This passes — stay hydrated and get extra salt.
Days 6-7: Entering Ketosis
Ketone production increases. You may notice reduced hunger, more stable energy, and possibly fruity breath or a metallic taste.
Weeks 2-4: Fat Adaptation
Your body becomes efficient at using fat for fuel. Energy improves, hunger decreases significantly, and mental clarity often increases.
Managing Keto Flu
The "keto flu" isn't actually flu — it's your body adjusting to using fat instead of glucose. Symptoms are often due to electrolyte loss. To minimise discomfort:
Drink plenty of water — You'll urinate more as glycogen releases water
Add salt liberally — Low-carb eating causes sodium excretion; add 1-2 teaspoons of salt daily
Eat potassium-rich foods — Avocados, leafy greens, fish
Consider magnesium — Many people are deficient; supplements can help with cramps and sleep
Keto Shopping List for UK Supermarkets
Here's what to pick up from Tesco, Sainsbury's, Asda, Lidl, and Aldi:
Proteins
- Beef mince (20% fat is fine on keto)
- Chicken thighs (fattier than breast)
- Streaky bacon and pork belly
- Salmon fillets and smoked salmon
- Eggs — as many as you like
Fats
- British butter (Lurpak, Anchor)
- Extra virgin olive oil
- Coconut oil
- Double cream
Dairy
- Cheddar, brie, camembert, mozzarella
- Full-fat cream cheese (Philadelphia)
- Full-fat Greek yoghurt (check carbs)
Vegetables
- Broccoli, cauliflower, cabbage
- Spinach, rocket, lettuce
- Courgettes, mushrooms, peppers
- Avocados
Is Keto Right for You?
The keto diet can be particularly effective for:
- People who want maximum appetite suppression
- Those who struggle with constant hunger on other diets
- People who respond well to clear, simple rules
- Those with blood sugar regulation issues (consult your GP first)
Keto may not suit:
- High-performance athletes who need glycogen for explosive activities
- People who can't give up bread, pasta, and fruit
- Those with certain medical conditions (kidney disease, pancreatitis)
- Pregnant or breastfeeding women (consult your GP)
Important: Consult Your GP
If you take medications — especially for diabetes, blood pressure, or other conditions — speak to your GP before starting keto. Medication doses may need adjusting as your blood sugar and blood pressure can change significantly.
Tracking Your Keto Macros
Success on keto often comes down to accurate tracking, especially in the beginning. Key tips:
- Focus on net carbs — Total carbs minus fibre. Aim for under 20-25g net carbs initially.
- Hit your protein target — Usually 1.2-2g per kg of body weight. Don't under-eat protein.
- Fat is a lever — Eat enough fat to feel satisfied, but you don't need to hit a fat "goal" if trying to lose weight.
- Use a tracking app — NutraSafe tracks all macros with UK foods and barcode scanning.