Intermittent fasting and keto are both popular ways to support your metabolism and manage your weight, but they work in different ways. Intermittent fasting is about when you eat, while keto is about what you eat.
Any dietary pattern will work differently for different people. In general, choosing a plan that aligns with your daily habits, food preferences, and nutritional needs is more likely to help you achieve lasting results.
Intermittent fasting:
- You may eat less overall by eating only during certain times. You lose weight when you use more calories than you eat.
- It also keeps your insulin levels lower for longer, which can help your body burn stored fat.
- You can eat a wider variety of foods, which might make it easier to stick with for a long time. Keto cuts out entire food groups, so it can feel more limiting and harder to stick to.
Keto:
- You eat more fat and protein, which helps you feel full and eat less.
- Because your body uses more fat for energy in ketosis, some people notice faster weight changes, especially in the first weeks when you lose water and fat.
Intermittent fasting, or time-restricted eating, focuses on when you eat rather than cutting out certain foods.
The most common intermittent fasting methods include:
- The 16:8 approach: Fasting for 16 hours and eating within an 8-hour window.
- The 5:2 approach: Eating normally five days per week and limiting calories on two days.
- Alternate-day fasting: Fasting one day and eating regularly the next.
Your body usually gets energy from glucose, or sugar, in your food. When you fast for a while, your body runs out of glucose and starts burning fat for energy. This change can help with weight loss and other health benefits.
While you’re fasting, you can still have water, black coffee, or unsweetened tea. Intermittent fasting may help you eat fewer calories overall and improve how your body uses insulin. Research shows intermittent fasting can:
- Promote weight loss
- Help control blood sugar
- Improve heart health when combined with balanced meals
Even though intermittent fasting doesn’t cut out certain foods, it’s still important to eat healthy, nutrient-rich foods during your eating times to ensure your body gets the nutrients it needs for overall health.
The ketogenic diet, (keto) is high in fat and very low in carbs. People on keto often eat foods like meat, fish, eggs, cheese, nuts, seeds, oils, and low-carb vegetables.
In a typical keto diet, about 90% of your calories come from fat, 6% from protein, and only 4% from carbs. You avoid or limit foods high in carbs, such as bread, rice, pasta, most fruits, and starchy vegetables.
If you eat less than about 50 grams of carbs a day, your body enters a state called ketosis. In ketosis, your liver changes fat into ketones, which your body then uses for energy instead of sugar from carbs.
The keto diet can help you lose weight quickly at first, mostly from water loss, and then from losing fat over time. Studies show the keto diet may help:
Long-Term Considerations of Keto
Staying on keto for a long time can raise the risk of:
- Nutrient deficiencies: Keto cuts out many foods that provide fiber and important nutrients, such as whole grains, beans, most fruits, and some vegetables. This can make you more likely to miss out on vitamins and minerals.
- High cholesterol: Eating too much fat for a long time can raise low-density lipoprotein (LDL) cholesterol in some people, which can increase the risk of heart disease.
- Kidney stones: Keto can alter your body’s mineral and fluid balance, which may increase your risk of kidney stones.
- Weight cycling: Many people find it hard to stick with keto for a long time, so they lose and regain weight. This weight cycling can raise the risk of high blood pressure, high cholesterol, and kidney or liver problems.
Long-Term Considerations of Intermittent Fasting
Some possible long-term benefits and concerns are:
- Metabolic health: Studies show that intermittent fasting can improve insulin sensitivity, blood pressure, and cholesterol if you eat healthy meals during your eating times. These changes may help lower the risk of heart disease and type 2 diabetes.
- Cell repair: Fasting triggers a process called autophagy, in which your body breaks down and recycles damaged cells. This might help with healthy aging, but researchers are still learning about the long-term effects in people.
- Heart health risks with very short eating windows: Studies suggest that eating in less than an eight-hour window each day may raise the risk of heart-related death for some people, especially those with heart disease or cancer.
Doing both intermittent fasting and keto at the same time can help your body enter ketosis faster and may lead to faster short-term fat loss. This is usually safe for a short time, but it can raise the risk of side effects like:
- Fatigue
- Dizziness
- Headaches
- Constipation
When you limit both when and what you eat, it can be difficult to get enough fiber, vitamins, and minerals each day. Doing both diets together can also feel more limiting and harder to stick with over time. Before you start both keto and intermittent fasting, check with a healthcare provider.
