Carb Tolerance On Keto: How Much Is Too Much?

The ketogenic diet is a low-carb, high-fat eating plan that promotes ketosis, a metabolic state where the body relies on fat for fuel instead of carbohydrates. While the keto diet is a popular approach for weight loss and improved health, determining one's carb tolerance is crucial to achieving and maintaining ketosis. This involves understanding individual differences in metabolism, insulin sensitivity, activity levels, body composition, and medical conditions. By experimenting with different carb levels and tracking physical and mental responses, individuals can find their optimal carb intake for ketosis. This process may include using tools like a Continuous Glucose Monitor (CGM) and making gradual adjustments to the diet.

The role of insulin resistance in determining carb tolerance

Insulin resistance is a metabolic disorder that is becoming more common worldwide and is linked to some of the most prevalent diseases in modern societies, such as diabetes, hypertension, obesity, and coronary heart disease. It occurs when the body resists insulin's signal to store glucose, resulting in high blood sugar levels. While insulin resistance is caused by a variety of factors, including visceral fat accumulation, chronic inflammation, high-fat and high-sugar diets, sleep deprivation, and chronic stress, dietary carbohydrates play a significant role in its development.

The relationship between dietary carbohydrate intake and insulin resistance is complex and remains an active area of research. Epidemiological studies suggest that total dietary carbohydrate intake does not predict the risk of type 2 diabetes. In fact, high-carbohydrate, high-fibre diets with a low glycaemic index may even contribute to diabetes prevention. However, the type of carbohydrate consumed appears to be important. Simple sugars, particularly fructose, have been shown in animal studies to have adverse effects on insulin action, while increased intake of dietary fibre may improve insulin action and protect against diabetes development.

The effects of diet composition on insulin resistance have been studied, with some evidence suggesting that low-carbohydrate diets can improve insulin sensitivity. For example, a review found that low-carbohydrate diets were more effective than low-fat diets in improving insulin resistance, but it is important to note that the "low-carb" diets in these studies still included around 40% carbohydrates. This highlights that even a moderate reduction in carbohydrate intake can have benefits for insulin sensitivity.

The ketogenic diet, a high-fat, low-carbohydrate approach, has gained popularity for its potential to improve insulin resistance and manage blood sugar levels. By severely limiting carbohydrate intake, the body is forced to use ketones produced by the liver as an alternative energy source. This transition to a ketogenic state can take anywhere from two days to two weeks, depending on the individual. While the ketogenic diet can be effective, it is not a one-size-fits-all solution, and some individuals may find they can tolerate more carbohydrates than others.

In summary, insulin resistance is influenced by a combination of factors, including dietary carbohydrates. While reducing carbohydrate intake can be beneficial for improving insulin sensitivity, it is not the only factor to consider. Visceral fat, chronic inflammation, stress, sleep, and the type of carbohydrates consumed also play a role in insulin resistance. Therefore, addressing these factors through dietary and lifestyle modifications can help improve insulin sensitivity and manage blood sugar levels effectively.

How to measure your glucose response to carbs

Oral Glucose Tolerance Test (OGTT)

The OGTT is considered the gold standard for assessing your metabolic response to carbs. To perform the test, you drink a glucose solution and record your blood glucose levels in the hours that follow. Clinicians use OGTT results to quantify diabetes risk. Here’s how they interpret the results:

• Normal: under 140 mg/dl
• Prediabetes: between 140 mg/dl and 200 mg/dl
• Diabetes: over 200 mg/dl

Real-world glucose testing

The OGTT may be useful, but it has limited real-world applicability as most people don't consume pure glucose. To perform your own glucose test, measure your blood sugar before eating and then consume a carbohydrate-containing meal. Measure your glucose again at one hour and two hours after the meal.

Testing at your doctor's office

Your primary care physician, endocrinologist, or weight loss doctor may order fasting insulin, fasting glucose, or a Hemoglobin A1c (HbA1c) test to assess your blood sugar during your office visit. A HbA1c of 5.7-6.4 indicates pre-diabetes, while an HbA1c of 6.5+ is diagnostic of type 2 diabetes. Elevated fasting insulin or fasting blood sugar levels can also be indicative of your level of carb tolerance.

Continuous Glucose Monitor (CGM)

A Continuous Glucose Monitor is a small monitor that painlessly attaches to your arm and continually records your blood sugar level. The accompanying app provides a clear visual map of how your body handles carbohydrates throughout the day. With this device, you can watch in real-time how your body reacts to foods, eliminating grey areas such as keto snacks or dark chocolate.

Bathroom scale

The easiest way to let the scale guide you to your carb tolerance is to use a step-down method. Record your daily carb intake and step down or reduce the amount to achieve your desired result.

How to improve your carb tolerance

Carb tolerance, or your body's ability to metabolise and digest carbohydrates, is an important aspect of your health. If you're looking to improve your carb tolerance, here are some tips to help you get started:

Exercise

Physical activity increases your body's ability to regulate glucose and insulin levels. This means you can consume more carbs while maintaining metabolic health.

Get Good Sleep

A well-rested body helps insulin do its job. Aim for 7-9 hours of restful sleep per night to support healthy glucose regulation.

Manage Stress

The stress hormone cortisol can elevate blood sugar and hinder fat burning. Find what works for you to manage stress, such as exercise, meditation, yoga, or spending time with loved ones.

Eat Fibre-Rich Carbohydrates

Consuming fibre along with starch and sugar helps blunt the blood sugar spike. Opt for fruits and vegetables as your primary sources of carbohydrates.

Experiment with Different Carbohydrates

Monitor how various carbs like rice, sweet potatoes, and apples affect your blood sugar, digestion, and energy levels. You may find that certain carbs agree with your body better than others.

Try a Ketogenic Diet

Consider trying a very low-carb ketogenic diet, which has been shown to improve glucose regulation in obese and diabetic populations. This may also aid in weight loss, gut health, and mental clarity.

Intermittent Fasting

Intermittent fasting has metabolic effects similar to the keto diet, improving glucose regulation and giving your gut time to heal. This may increase your tolerance for a variety of foods.

Step-Down Your Carb Intake

Gradually reduce your carb intake over time to give your body and mind time to adjust. This can help you find your ideal carb tolerance level, which may be in the low-carb range of 50-125 grams per day or the keto range of less than 50 grams.

Listen to Your Body

Pay attention to how you feel after eating carbs. Mental fog, fatigue, and intense cravings may indicate that you're consuming too many or poor-quality carbs.

Use a Continuous Glucose Monitor (CGM)

A CGM is a small monitor that attaches to your arm and records your blood sugar levels throughout the day. This tool can help you understand how your body handles carbs and identify hidden sugars or carbohydrates in your diet.

Use Your Bathroom Scale

Compare your daily carb intake with the results on the scale. This can help you determine if your carb intake is aligned with your weight management goals.

Remember, everyone's carb tolerance is unique and influenced by factors like age, activity level, past diet, health history, and genetics. By implementing these strategies, you can work towards improving your carb tolerance and finding the right balance for your body.

The oral glucose tolerance test (OGTT)

To perform the test, a patient is asked to take a glucose drink and their blood glucose level is measured before and at intervals after the drink is consumed. The intervals can be regular, such as every 30 or 60 minutes, or a single test can be done after two hours. The test could take up to three hours. It is recommended that the patient has something to occupy themselves with during the waiting periods, such as reading material.

Clinicians use OGTT results to quantify diabetes risk. Here is how they stratify risk at the two-hour post-test mark:

• Normal: under 140 mg/dL
• Prediabetes: between 140 mg/dL and 200 mg/dL
• Diabetes: over 200 mg/dL

It is important to note that the World Health Organization (WHO) recommends consuming at least 150 grams of carbohydrates for three days preceding the OGTT, but some evidence suggests this is unnecessary.

How to step down your carb intake

To determine your carb tolerance on keto, you must first understand how the keto diet works. The keto diet is a low-carb, high-fat diet that puts your body into a metabolic state called ketosis. In this state, your body uses fat and ketones instead of glucose as its main fuel source. To achieve ketosis, you need to consume very few carbs, typically less than 50 grams of net carbs per day, and sometimes as low as 20 grams. Net carbs are calculated by subtracting the amount of fibre and half the amount of sugar alcohols from the total number of carbs.

• Gradually reduce your carb intake: Start by eliminating one type of high-carb food at a time, such as bread or sugary drinks. This gradual approach will help you adjust to the diet more easily.
• Focus on whole, unprocessed foods: Choose carbs from whole, unprocessed sources such as vegetables, nuts, and seeds. These foods provide essential vitamins and minerals and are more filling than processed carbs.
• Increase your fat intake: The keto diet is a high-fat diet, so make sure to include plenty of healthy fats such as olive oil, avocado, nuts, and fatty cuts of meat. This will help you feel more satisfied and provide the energy your body needs.
• Choose your protein sources wisely: Include moderate amounts of protein in your diet, as too much protein can prevent ketosis. Good sources of protein on the keto diet include meat, fish, tofu, and eggs.
• Plan your meals: Create a simple meal plan for the week that includes keto-friendly foods. This will help you stay organised and ensure you're getting the right balance of nutrients.
• Monitor your health: Regularly check your health, including your heart health and blood sugar levels, especially if you have diabetes. This will help you understand how the keto diet is affecting your body.
• Consult a healthcare professional: Before making any significant dietary changes, it's important to consult a doctor or dietitian. They can provide personalised advice and ensure that the keto diet is safe for you.

Frequently asked questions