Which vegetables are not allowed on keto and why?

October 28, 2025 •

4 min read

Many keto dieters are surprised to learn that some otherwise healthy vegetables, like potatoes and corn, are strictly off-limits due to their high carbohydrate content. It's essential to know precisely which vegetables are not allowed on keto to successfully maintain ketosis and achieve your health and weight loss goals. This guide breaks down the specific culprits and the reasons behind the restrictions.

Quick Summary

An effective keto diet requires avoiding high-carb vegetables to maintain ketosis. This includes high-starch root vegetables, legumes like peas, and corn. Mindful consumption of other moderate-carb options is also key.

Key Points

Avoid High-Starch Vegetables: Vegetables high in starch like potatoes, sweet potatoes, and corn are not allowed on a ketogenic diet because their carbohydrate content will exceed daily limits and disrupt ketosis.
Limit Certain Root Vegetables: Some root vegetables and produce with higher natural sugar content, such as carrots, beets, and winter squashes, should be consumed only in careful moderation.
Focus on Net Carbs: Success on keto depends on tracking net carbs (total carbs minus fiber). Vegetables high in fiber have less impact on blood sugar.
Prioritize Above-Ground Vegetables: As a general rule, leafy greens and other vegetables that grow above ground are excellent keto choices due to their lower carbohydrate and higher fiber content.
Replace High-Carb Veggies with Alternatives: Use keto-friendly substitutes like cauliflower for mashed potatoes or rice, and zucchini for pasta to enjoy your favorite meals without the carbs.
Watch Out for Legumes: High-carb legumes, including peas, beans, and lentils, are generally avoided on keto despite their other health benefits.

The Core Reason: Why High-Carb Vegetables Are Restricted

The ketogenic diet is fundamentally designed to force the body into a metabolic state called ketosis, where it burns fat for fuel instead of glucose (sugar) from carbohydrates. To achieve this, carbohydrate intake must be severely restricted, typically to 20–50 grams of net carbs per day. While vegetables are generally healthy, their carbohydrate content varies drastically. High-starch vegetables can quickly push a person over their daily carb limit, halting the fat-burning process and ending ketosis.

The key metric to consider is net carbs, which is calculated by subtracting dietary fiber from the total carbohydrates. Fiber is a carbohydrate that the body cannot digest, so it doesn't impact blood sugar levels in the same way as starches and sugars. This is why low-carb vegetables, which are often high in fiber, can be eaten more freely on a keto diet.

Starchy Root Vegetables: The Highest Carb Offenders

Many vegetables that grow underground, particularly those that store energy in the form of starch, contain a high concentration of carbohydrates. Consuming even a small portion of these can use up a significant portion of a keto dieter's daily carb allowance, making them a no-go for strict keto.

Here are some of the highest-carb root vegetables to avoid:

Potatoes: This includes all varieties—white, russet, and red potatoes. A single medium potato contains more than the daily carb limit for many on keto.
Sweet Potatoes and Yams: Despite being a nutritional powerhouse, these are loaded with carbohydrates and are not suitable for a ketogenic diet.
Parsnips: A starchy root vegetable with a high sugar content, making it another one to avoid.
Cassava (Yuca): An extremely starchy root vegetable that should be completely avoided on keto.
Turnips and Rutabagas: While lower in carbs than potatoes, they are still considered high-carb and should be avoided on a strict keto diet.

Legumes and Grains to Avoid

Though not always classified as vegetables, some legumes and grains are often mistaken for keto-friendly options. They are, however, notoriously high in carbohydrates and should be avoided.

Corn: A common grain, corn and its derivatives (cornmeal, popcorn) are packed with carbs and will quickly kick you out of ketosis.
Peas: While small, green peas contain a surprising amount of starch. A single cup of green peas can account for more than half of a daily carb allowance on strict keto.
Beans and Lentils: Most beans and lentils, including black beans, chickpeas, and lentils, are high in carbs and fiber, but the net carb count is still too high for a ketogenic diet.

Vegetables to Enjoy in Moderation

Some vegetables contain a moderate amount of carbohydrates and can be included in a keto diet, but only in very limited quantities. Portion control is key to ensure you do not exceed your daily net carb goals. A general rule is to be more cautious with sweeter or more colorful vegetables.

Carrots: Contain a moderate amount of carbs and sugar. Small portions can be included in a meal, but consuming them raw is better as cooking can affect their glycemic impact.
Beets: These root vegetables are higher in sugar than many other keto-friendly options and should be limited.
Onions: While a common aromatic, large amounts of onions can add up in carbs. A small amount for flavor is generally fine, but piling them on is not recommended.
Winter Squashes: Varieties like butternut squash and acorn squash are higher in carbs than their summer counterparts and should be used sparingly.

Comparison of High-Carb vs. Low-Carb Vegetables


Vegetable Type	High-Carb (Avoid/Limit)	Typical Net Carbs (per 100g)	Low-Carb (Keto-Friendly)	Typical Net Carbs (per 100g)
Root Vegetables	Potatoes, Sweet Potatoes, Yams, Parsnips	~15-30g	Radishes, Celery Root (Celeriac)	~2-6g
Legumes/Grains	Corn, Peas, Black Beans	~9-20g	Green Beans, Black Soybeans	~3-5g
Bulbs/Tubers	Onions (in large amounts), Leeks	~8-12g	Garlic, Scallions	~1-2g
Squash	Butternut, Acorn	~10-15g	Zucchini, Cucumber, Pumpkin (in moderation)	~3-4g
Greens	N/A	N/A	Spinach, Kale, Lettuce, Swiss Chard	~1-3g
Cruciferous	N/A	N/A	Broccoli, Cauliflower, Cabbage, Brussels Sprouts	~3-5g

Keto-Friendly Alternatives: Focus on Above-Ground and Leafy Greens

To ensure adequate vitamin and mineral intake without compromising ketosis, you can eat a wide variety of low-carb, above-ground vegetables. These options are typically higher in fiber and lower in starch.

Leafy Greens: Spinach, kale, lettuce, collard greens, and arugula are excellent choices and can be consumed in larger quantities.
Cruciferous Vegetables: Broccoli, cauliflower, Brussels sprouts, and cabbage are versatile and low in carbs.
Squash: Summer squashes like zucchini and yellow squash are very low-carb and can be used as alternatives to pasta or potatoes.
Asparagus: A classic keto-friendly vegetable that is both nutritious and low in net carbs.
Bell Peppers: All colors are suitable, but green peppers are slightly lower in carbs than red or yellow.
Mushrooms: All types of mushrooms are low in carbs and add a great savory flavor to meals.
Celery and Cucumber: Excellent, refreshing snacks or additions to salads due to their high water content and minimal carbs.

Conclusion: Navigating Vegetables for Keto Success

Successfully adhering to a ketogenic diet requires careful attention to your total carbohydrate intake, and that includes carbs from vegetables. The key is to avoid high-starch, high-sugar vegetables and legumes while focusing on the wide array of delicious, nutrient-dense, low-carb options like leafy greens and cruciferous vegetables. By being mindful of which vegetables are not allowed on keto and understanding why, you can better manage your macronutrient targets and stay firmly in ketosis. Always prioritize nutrient-rich foods that fit your carb budget to maintain a healthy and sustainable diet.

For more detailed information on which vegetables are best, refer to guides on low-carb vegetables and the general rules of keto diets, including resources like Healthline's review on low-carb vegetables.

Frequently Asked Questions

Potatoes are not allowed on the keto diet because they are a starchy root vegetable with a very high carbohydrate content. A single medium potato can contain enough carbs to use up an entire day's carb allowance, which will prevent or end ketosis.

No, corn is not suitable for a keto diet. It is a grain and, like other starchy vegetables, is very high in carbohydrates, making it a forbidden food for maintaining ketosis.

Peas are generally not recommended on a strict keto diet due to their high starch content. A cup of green peas contains a significant amount of carbs, which can easily derail your progress.

Carrots can be included in a keto diet, but only in moderation and small quantities. While healthier than potatoes, they still contain a moderate amount of sugar and carbohydrates, so portion control is essential.

Plants store energy in their roots in the form of starches and sugars. This is why root vegetables like potatoes, parsnips, and beets are naturally higher in carbohydrates than leafy greens or above-ground vegetables.

The best vegetables for a keto diet are typically low-carb, above-ground varieties like spinach, kale, broccoli, cauliflower, zucchini, bell peppers, asparagus, and cucumber.

Yes, there are many great substitutes. For example, use riced cauliflower or mashed cauliflower instead of rice and potatoes, and spiralized zucchini or spaghetti squash instead of pasta.