A keto diet plan is a high-fat, very-low-carbohydrate eating pattern designed to shift your body’s primary fuel source from sugar to fat. The standard version calls for roughly 70 to 80 percent of your daily calories from fat, 10 to 20 percent from protein, and just 5 to 10 percent from carbohydrates. On a 2,000-calorie day, that translates to about 20 to 50 grams of carbs, which is less than what you’d find in a single bagel.
How Ketosis Works in Your Body
When you cut carbohydrates drastically, your body runs low on its preferred fuel: glucose. Within two to four days (sometimes up to a week), your liver begins breaking down stored fat into molecules called ketone bodies, which your brain, heart, and muscles can use for energy instead. This metabolic state is called ketosis.
The process unfolds in a specific way. Your fat cells release stored fatty acids into the bloodstream. Those fatty acids travel to the liver, where they’re broken apart into a building block called acetyl-CoA. Normally the liver would burn acetyl-CoA through its regular energy cycle, but with so little carbohydrate available, that cycle can’t keep up. The overflow gets converted into ketone bodies and released into your blood, effectively turning your body into a fat-burning machine. As long as you keep carbs low enough, this process continues.
Three Versions of the Keto Diet
Not everyone follows the same version. The plan you choose depends on how active you are and what kind of exercise you do.
- Standard Ketogenic Diet (SKD): The most common approach. You keep carbs at or below 30 grams per day at all times. This works well if your activity level is low to moderate, such as walking, yoga, cycling, or light weightlifting.
- Targeted Ketogenic Diet (TKD): You follow the standard plan most of the time but eat a small amount of carbs 30 to 60 minutes before intense workouts. This gives you quick fuel for high-intensity exercise without knocking you out of ketosis for long. It’s a good option if you exercise hard but don’t want full carb-loading days.
- Cyclical Ketogenic Diet (CKD): You eat standard keto most of the week, then do one or two days of higher carbohydrate intake to fully refill your muscle glycogen stores. This version is typically used by bodybuilders or competitive athletes whose training volume is too high to sustain on fat alone.
If you’re new to keto and not doing intense training, the standard version is the place to start.
What to Eat on Keto
The bulk of your plate will be fat and protein. Eggs are a staple: a single egg provides about 5 grams of fat and 7 grams of protein with virtually no carbs. Butter is carb-free and roughly 80 percent fat. Seeds pack a surprising punch: a quarter cup of flax seeds delivers 18 grams of fat along with 11 grams of fiber, and three tablespoons of hemp hearts provide 15 grams of fat. Full-fat Greek yogurt offers 6 grams of fat and 13 grams of protein per serving, though it does contain about 6 grams of carbs, so it needs to be budgeted carefully.
Avocados, olive oil, coconut oil, fatty fish like salmon and sardines, cheese, and nuts round out the fat sources. For protein, think unprocessed meats, poultry, and seafood. The goal is moderate protein, not unlimited. Eating too much protein can actually interfere with staying in ketosis.
Vegetables That Fit
You can eat plenty of vegetables on keto, but you need to choose ones that are low in net carbs (total carbs minus fiber). Per 100 grams raw, these are some of the best options:
- Spinach: 1.4 g net carbs
- Asparagus: 2.0 g net carbs
- Romaine lettuce: 2.3 g net carbs
- Zucchini: 2.3 g net carbs
- Mushrooms: 2.8 g net carbs
- Cauliflower: 3.0 g net carbs
- Broccoli: 4.0 g net carbs
Cauliflower deserves special mention because it substitutes for rice, mashed potatoes, and even pizza crust. Cabbage (3.0 g net carbs) works well as a noodle replacement. These swaps make the diet feel less restrictive over time. Starchy vegetables like potatoes, corn, and sweet potatoes are off the table entirely.
Fiber on a Keto Diet
One challenge with cutting carbs so low is getting enough fiber. Most high-fiber foods, like whole grains and beans, are also high in carbohydrates. You’ll need to be intentional about including fiber-rich, low-carb options. Flax seeds, chia seeds (4 grams of fiber per tablespoon), and cacao nibs (9 grams of fiber per ounce) are some of the most efficient choices. Loading up on the low-carb vegetables listed above also helps. Spinach, broccoli, and cabbage all contribute fiber without pushing you past your carb limit.
The “Keto Flu” and What to Expect Early On
During your first week, there’s a good chance you’ll feel worse before you feel better. About 45 percent of people starting keto report flu-like symptoms: headache, fatigue, nausea, dizziness, brain fog, and low energy. Some people experience digestive discomfort or notice their heart rate feels different. These symptoms typically peak in the first week and taper off within four weeks. For many people, the worst passes in about four to five days.
The likely culprit is a shift in how your body handles water and electrolytes. When you cut carbs, your kidneys flush out more sodium, and with it, water. The most common remedies focus on replacing what you’re losing: increasing sodium intake, supplementing with magnesium and potassium, and drinking more water. Adding a pinch of salt to your water or drinking broth can make a noticeable difference during that first rough week.
Weight Loss: What the Evidence Shows
Keto does produce weight loss, but the advantage over other diets is smaller than many people expect. In systematic reviews of randomized controlled trials, people on ketogenic diets lost roughly 0.9 to 2.2 kg (about 2 to 5 pounds) more than people on low-fat diets over 6 to 24 months. One large trial of over 600 people found that the low-carb group lost 6.0 kg at one year compared to 5.3 kg for the low-fat group, a difference that wasn’t statistically significant.
Higher-quality studies tend to show little to no difference between keto and other calorie-controlled diets over the long term. The rapid early weight loss that makes keto feel so effective in the first few weeks is largely water. As your body depletes stored carbohydrate (glycogen), it releases the water that was bound to it. Fat loss follows, but at a pace more in line with other diets. Where keto may have a genuine edge is appetite suppression: many people report feeling less hungry on high-fat diets, which makes it easier to eat less without feeling deprived.
How to Know You’re in Ketosis
You can test your ketone levels three ways: blood, urine, or breath. Blood testing is the most accurate, especially for readings below 5 mmol/L. Nutritional ketosis generally starts at blood ketone levels around 0.5 to 0.6 mmol/L. Levels above 3.0 mmol/L are considered high and aren’t necessary for the diet’s benefits.
Urine strips are cheaper and easier but become less reliable over time. As your body gets better at using ketones for fuel, fewer spill into your urine, which can make it look like you’ve fallen out of ketosis when you haven’t. Breath meters measure acetone (a byproduct of ketone production) and offer a middle ground between convenience and accuracy. For most people, though, testing is optional. If you’re eating under 30 grams of carbs per day and experiencing reduced appetite and steady energy, you’re almost certainly in ketosis.
Long-Term Safety Considerations
Short-term use of the keto diet (a few months to a year) is generally well-studied and considered safe for most adults. Long-term data is more limited, but the evidence that does exist is reassuring in some respects. A published case report of a patient who followed a ketogenic diet for 10 years found no adverse effects on thyroid function, kidney function, or bone mineral density. LDL cholesterol did nearly double, but the increase was in large, buoyant particles rather than the small, dense type associated with heart disease risk. Triglycerides stayed low and HDL cholesterol stayed high.
That said, one case report isn’t a population study. The most common concerns with long-term keto include nutrient deficiencies (particularly if vegetable and fiber intake is low), elevated LDL cholesterol in some individuals, and the sheer difficulty of maintaining such a restrictive pattern for years. Many people cycle in and out of keto or use it as a short-term tool rather than a permanent lifestyle.