Last update: October 31, 2025
7 minute read
Keto Diet Guide: How the Ketogenic Diet Works, Benefits, and Risks
Curious if the ketogenic diet is right for you? Learn how keto works, what it does to your body, the potential benefits and risks, and whether this high-fat approach fits your lifestyle.
By Derick Rodriguez, Associate Editor
Edited by Dr. Dimitar Marinov, MD, RDN, PhD
Ever wonder why people are putting butter in their coffee and ordering burgers without buns? The ketogenic diet has moved from medical treatment rooms into mainstream culture, promising rapid weight loss and mental clarity.
But going keto isn't just about cutting carbs. It's a complete metabolic shift that changes how your body produces energy.
This guide walks you through the science behind ketosis, what happens in your body when you drastically cut carbs, and whether the potential benefits outweigh the risks.
Key takeaways
- Ketosis is a metabolic state where your body burns fat for fuel instead of glucose, achieved by eating fewer than 20-50 grams of carbs daily
- Weight loss happens fast initially due to water loss and reduced appetite, though long-term results vary widely
- Potential benefits extend beyond weight loss to blood sugar control, mental focus, and therapeutic uses for certain medical conditions
What is the ketogenic diet?
The ketogenic diet (or "keto") flips your normal food ratios upside down. Instead of eating mostly carbs, you eat mostly fat. Yes, fat.
Here's what your plate looks like:
- 70-80% fat: Butter, oils, fatty meats, avocados, cheese
- 15-20% protein: Meat, fish, eggs
- 5-10% carbohydrates: Mostly from vegetables
To put this in perspective, 50 grams of carbs is less than two slices of bread. Most people eat 200-300 grams daily.
The goal? Force your body into ketosis, where it stops using carbs (glucose) as the main source for energy and starts burning a significant amount of ketones as well.
Doctors created this diet in the 1920s to help kids with epilepsy. Today, most people try it for weight loss or increased energy.
How does ketosis work?
Think of your body like a hybrid car that runs on two fuels: glucose (from carbs) or ketones (from fat).
Normally, your body prefers glucose. But when you stop eating carbs, your glucose runs out in a few days.
The timeline
- Day 1: Your body uses stored glucose from muscles and liver.
- Day 2-3: Once glucose runs out, your liver starts breaking down fat into ketone bodies. These ketones power your brain, muscles, and organs.
- Day 4-7: You may lose high amount of electrolytes leading to the so-called “keto-flu”
- Week 1+: Your body gets better at using ketones and you feel more normal.
Signs you're in ketosis
- Bad breath (fruity or metallic)
- Increased thirst and urination
- Less hunger between meals
- Initial tiredness, then stable energy
Testing methods
Method | Cost | Accuracy |
|---|---|---|
Urine strips | $10-15 | Works at first, less accurate later |
Blood meter | $40+ for meter | Most accurate |
Breath analyzer | $100-200 one-time | Pretty accurate |
The goal is blood ketone levels of 0.5-3.0 mmol/L.
What can you eat on keto?
Bread, pasta, rice, potatoes, most fruits, and anything with sugar are off-limits.
Proteins:
- Beef, pork, lamb (fatty cuts)
- Chicken and turkey (with skin)
- Bacon, sausage
- Fatty fish (salmon, mackerel)
- Eggs
Fats:
- Butter, ghee
- Olive oil, coconut oil
- Heavy cream, cream cheese
- Hard and soft cheeses
Vegetables (low-carb):
- Leafy greens
- Broccoli, cauliflower
- Zucchini, cucumber
- Bell peppers
- Avocados
Extras:
- Nuts and seeds (limited)
- Dark chocolate (85%+, small amounts)
Foods to avoid:
- All grains and starches
- Sugar and sweets
- Most fruits (small berries okay)
- Beans and legumes
- Potatoes and root vegetables
- Low-fat products
- Most alcohol
VitaRx Tip
Restaurant meals are tricky on keto. Even grilled chicken might have sugary marinade. Always ask about ingredients.
Why do people lose weight on keto?
Week 1: Water weight
Your body stores carbs as glycogen, and each gram holds 3-4 grams of water. When glycogen depletes, that water leaves.
People often lose 5 pounds in the first week. This isn't just fat, it's mostly water.
The real fat loss reasons:
- Reduced hunger: Ketones suppress hunger hormones. Many people naturally eat less without trying.
- Stable blood sugar: No carb-driven insulin spikes means your body accesses stored fat more easily.
- Filling foods: Protein and fat keep you satisfied longer than carbs.
Reality check
Long-term weight loss still requires burning more calories than you eat. Keto makes this easier for many people, but it's not magic. Some people eat so much fat and cheese they stall or gain weight.
Benefits beyond weight loss
Blood sugar control
For people with type 2 diabetes or pre-diabetes, keto can dramatically lower blood glucose and insulin. Some reduce or eliminate medications under doctor supervision.
Mental clarity
Many report sharper thinking and stable energy without afternoon crashes. The brain runs efficiently on ketones.
Proven medical uses
- Epilepsy: The strongest scientific evidence. Can reduce seizures by 50%+ in drug-resistant cases.
- PCOS: Women with polycystic ovary syndrome sometimes see improved hormone balance and symptoms.
Being researched
- Anti-inflammatory effects
- Cancer therapy support (very early research)
- Brain health and Alzheimer's prevention
Most evidence beyond epilepsy comes from small studies or personal stories. Keto has legitimate uses but isn't a miracle cure.
— Dr. Dimitar Marinov, MD, RDN, PhDNutritionally, ketosis is achieved by cutting digestible carbs to roughly 20–50 g/day, which shifts fuel use toward fatty acids and ketone bodies. Over the long term, keto has no metabolic advantage—when calories and protein are matched, fat loss is comparable to other diets, so choose it only if the food pattern is sustainable for you.
What are the risks?
The keto flu (almost everyone gets this)
First 1-2 weeks you might experience:
- Headaches
- Nausea and fatigue
- Dizziness
- Irritability
- Brain fog
This happens because you're losing electrolytes with water weight, and your body hasn't adapted yet.
Common issues
- Nutrient deficiencies: Missing vitamins, minerals, and fiber from eliminated food groups.
- Digestive problems: Constipation is extremely common due to low fiber. Some get diarrhea from increased fat.
- Bad breath: Ketones expelled through lungs create distinctive fruity/metallic odor.
- Social challenges: Eating out is complicated. Social events revolve around foods you can't have.
Serious health risks
- Kidney stress (especially with kidney stones or disease)
- Liver concerns (works overtime producing ketones)
- Cholesterol changes such as elevated LDL (varies dramatically between people)
- Bone density loss (some studies show decreased density long-term)
Who should NOT do keto:
- Pregnant or breastfeeding women
- People with eating disorder history
- Anyone with pancreatic, liver, thyroid, or gallbladder problems
- People under 18 (unless medically supervised)
VitaRx Tip
If you take diabetes or blood pressure medication, talk to your doctor before starting. Keto can lower both, requiring medication adjustments to avoid dangerous drops.
Different types of keto
Standard Ketogenic Diet (SKD)
- Very low carb, moderate protein, high fat all the time.
- Best for: Beginners, weight loss focus
Cyclical Ketogenic Diet (CKD)
- 5 days keto, 2 days higher-carb.
- Best for: Athletes, bodybuilders
Targeted Ketogenic Diet (TKD)
- Small carbs (15-30g) around workouts only.
- Best for: Active people, gym-goers
High-Protein Ketogenic Diet
- 35% protein instead of 20%.
- Best for: Muscle preservation concern
Start with standard keto before trying variations.
Get your personalized vitamin recommendations in less than 3 minutes.
Get your personalized vitamin recommendations in less than 3 minutes.
Dos and don'ts of starting a keto diet
Do’s
Track food carefully at first
Add salt and electrolyte supplements
Drink 8-10 glasses of water daily
Eat vegetables within carb limit
Give it 4-6 weeks before judging
Consult doctor if on medications
Don’ts
Jump in without research
Ignore the keto flu
Assume all low-carb foods are keto-friendly
Overdo protein
Quit after a few bad days
Start if pregnant or have health issues
Frequently asked questions (FAQ)
Here are some of the most frequently asked questions about the keto diet.
Final thoughts
The ketogenic diet fundamentally changes how your body produces energy. For some, this brings rapid weight loss, better blood sugar control, and mental clarity. For others, it brings unsustainable restrictions and misery.
Keto isn't magic and isn't right for everyone. The science supporting medical uses (epilepsy, diabetes management) is solid. The hype as a universal solution? Oversold.
Go in with realistic expectations. The first couple weeks might be rough. Most people can't maintain it forever. Be honest about whether this restriction level fits your life.
Your health goals matter, but so does finding an eating pattern you can actually stick with. The "best" diet is the one you can maintain consistently while feeling good and reaching your goals.
VitaRx is here to help you navigate your options with evidence-based information so you can make informed choices about your health.
Sources and references
Editor
Derick Rodriguez
Derick Rodriguez focuses on editing health and wellness-related content. With over half a decade of experience in the digital realm, Derick has developed a unique skill set that bridges the gap between complex health concepts and accessible, user-friendly communication. His approach is deeply rooted in leveraging personal experiences and insights to illuminate the nuances of health and wellness topics, making them more approachable and empowering readers with knowledge and confidence.
Fact checker
Dr. Dimitar Marinov
Dr. Marinov has years of experience in scientific research and preventive and clinical medicine. His publications in peer-reviewed journals are on nutritional status, physical activity, and musculoskeletal disorders among adolescents.
At VitaRx, we're not just passionate about our work — we take immense pride in it. Our dedicated team of writers diligently follows strict editorial standards, ensuring that every piece of content we publish is accurate, current, and highly valuable. We don't just strive for quality; we aim for excellence.
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