Low-Carbohydrate Nutrition Approaches in Patients with Obesity, Prediabetes and Type 2 Diabetes

Publication Date: February 3, 2020
Last Updated: May 27, 2022

Authors: Lydia Bazzano, M

Lydia Bazzano, MD, PhD
Mark Cucuzzella, MD, FAAFP
Eric Westman, MD, MHS
William Yancy, MD, MHS



Prevalence of Target Diseases

  • The prevalence of prediabetes and type 2 diabetes has increased dramatically over several decades in parallel with the increasing prevalence of obesity.
  • Most recent estimates in 2015 state that 34% of Americans have prediabetes (hemoglobin A1c 5.7-6.4%) and 9.4% have type 2 diabetes (hemoglobin A1c ≥6.5% or on diabetes medication).
  • Obesity, prediabetes and type 2 diabetes are all risk factors for cardiovascular disease (CVD), and their increasing prevalence is now leading to an increase in the prevalence of CVD.

Key Points and Scope

  • Low-carbohydrate eating patterns are recognized in scientific literature and expert treatment guidelines as effective nutritional therapies for obesity, prediabetes and type 2 diabetes.
  • Because low- and very-low-carbohydrate eating patterns are effective treatments for these risk factors, plus risk factors such as hypertriglyceridemia and low high density lipoprotein (HDL) cholesterol (metabolic syndrome), their use has real potential for reducing CVD.
  • Low- and very-low-carbohydrate eating patterns can have potent lowering effects on blood glucose and blood pressure, which can lead to hypoglycemia or hypotension in people taking diabetes or blood pressure medications, respectively. Therefore, medication reduction, or deprescribing, is often required at the onset of dietary change, as is ongoing monitoring and medication management.
  • Numerous additional nuances to the use of these nutritional approaches have led to the production of this pocket guide, which is intended to assist practitioners in the safe and effective use of low-carbohydrate nutrition.
  • This pocket guide will define and describe low-carbohydrate nutritional approaches, identify appropriate target patient populations, and summarize recommended practices for the use of such eating patterns in adults, particularly adults with obesity, prediabetes or type 2 diabetes.
  • This pocket guide is not intended for treatment of children or people with type 1 diabetes, who may require adjustments to the approaches described.



Vital Sign Essentials

  • Weight
  • Height
  • Waist circumference
    • Start at the top of the hip bone, then bring the tape measure all the way around the body, level with the umbilicus. The patient can hold the beginning of the tape measure at the umbilicus and rotate 360⁰ in front of you to accomplish this.
    • Make the tape snug but not tight and record the measurement right after exhalation.
      Note: if waist circumference multiplied by 2 is greater than the patient's height, then risk is higher for metabolic syndrome. Use the same unit of measurement for both (e.g., inches).
  • Blood pressure and heart rate
    • Patient should be seated, relaxed, and rested for 5 minutes prior to measurement. Use appropriate sized cuff, as a cuff that is too small falsely elevates the reading.
      Note: Many patients with diabetes have stiff arteries due to arteriosclerosis, which can cause a falsely elevated blood pressure reading.

Basic Level Tests (consider for all)

  • Complete blood count (CBC)
  • Fasting complete metabolic panel (CMP), including: glucose, electrolytes, kidney function, bicarb for acid/base balance, liver panel
  • Fasting lipid panel, including: TC, HDL, LDL, triglycerides with attention to the TG/HDL ratio and TC/HDL ratio
  • Strongly consider screening all patients with obesity and type 2 diabetes for sleep apnea (home screening options readily available)
  • Strongly consider screening for food and sugar addiction
  • Thyroid-stimulating hormone (TSH)
  • Hemoglobin A1c (HbA1c)
  • Urine microalbumin (for patients with diabetes not taking ACE inhibitors or ARBs)

Second Level Tests (consider for higher risk groups)

  • 75 or 100 gram oral glucose tolerance test (OGTT)
  • Postprandial glucose and insulin tests
    • with or without insulin test
  • Advanced lipid profile to provide LDL particle size and number (large size and small number are desirable)
  • Coronary artery calcium (CAC) score to quantify coronary artery disease
  • Serum uric acid
  • Serum ferritin for iron stores (especially if vegetarian, low red meat consumption, or status post gastric bypass)
  • Vitamin B12 (especially if vegetarian, on long-term metformin use, or status post gastric surgery)
  • Vitamin D (especially if status post gastric surgery)
  • High-sensitivity C-reactive protein (hsCRP) to check systemic inflammation
  • C-peptide levels (consider for patients who have been on long-term insulin to ensure that the patient is still making insulin, especially if the patient does not fit the typical pattern of hyperinsulinemia)
  • Body composition scale that can accurately estimate visceral fat

Continuous Glucose Monitor (CGM)

  • CGM technology has become more accessible, affordable, and user friendly over time.
  • Reactive hypoglycemia and large post-meal spikes are common with standard high carbohydrate dietary patterns, both in insulin resistance and in later stage T2D with beta cell insufficiency. The CGM shows these patterns and how an individualized nutrition regimen improves them.

Patient Selection

  • Patients are good candidates for some type of carbohydrate-restricted dietary intervention if they have a problem with overweight, obesity or another metabolic problem.
  • Patients should be able and prepared to use a blood glucometer to check serum glucose if on insulin or insulin secretagogues (sulfonylureas and meglitinides) and to communicate with the health care team during the dietary intervention.
  • In most cases, patients with an acute, unstable medical condition are not candidates for any dietary intervention.
  • Co-existing conditions such as pregnancy or kidney or liver disease may require additional dietary changes or even interdict certain regimens.

Description of Approaches

Description of Approaches

Table 1. Low-Carb Eating Patternsa

Having trouble viewing table?
Eating Pattern Total Carbs
Meat Poultry Fish & Shellfish Eggs Tofu
Very Low-Carb Keto ≤30c No limitd No limitd No limitd No limitd
Low-Carb Keto 30–50c No limitd No limitd No limitd No limitd
Mediterranean 50–150 No limitd No limitd No limitd No limitd No limitd
Paleoe 50–150 No limitd No limitd No limitd No limitd
Primale 50–150 No limitd No limitd No limitd No limitd
Vegetarian 100–150 No limitd No limitd
Eating Pattern Total Carbs
Non Starchy Veggies Starchy Veggiesb Leafy Greens Berries Fruit Grains
Very Low-Carb Ket ≤30c 1 cup 2 cups
Low-Carb Keto 30–50c 2 cups 1 cup 2 cups ½ cup 1 cup
Mediterranean 50–150 3 cups 1 cup No limitd 1 cup 1 cup 2 svgs
Paleoe 50–150 3 cups 1 cup No limitd ½ cup ½ cup
Primale 50–150 3 cups 1 cup No limitd
Vegetarian 100–150 No limitd No limitd No limitd 1 cup 1 cup 4 svgs
a This table is based on the most common approaches, and some variants of each nutritional approach may differ slightly from the table.
b Examples are potatoes, corn, peas, beans/legumes, acorn or butternut squash, carrots, parsnips.
c Suggest a minimum of 15 grams total carbs daily in the form of non-starchy vegetables.
d May be consumed to satiety. While no limit is specified for these foods, consuming them excessively or beyond satiety can adversely impact weight management.
e Paleo/Primal food quality emphasized: grass-fed beef, grass-fed butter, limiting omega-6 fatty acids (vegetable oil, seed oil). Major difference between the two is that Primal allows dairy, nightshade vegetables and legumes.

Table 2. Selected Categories of Foods

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Foods with 0 carbs:
beef fish (e.g., tuna, salmon, catfish, bass, trout) veal
pork shellfish (e.g., shrimp, scallops, crab and lobster) sausage
bacon eggs lamb
chicken pork rinds ham
turkey pepperoni slices salami
duck (or other fowl) hot dogs bologna
Sweets with 0 carbs:
sugar-free gelatin
Sweets with < 5 carbs/serving:
sugar-free pudding low-carb protein shakes
Foods with ≤ 2 grams carbs but high calorie, so limit for weight loss:
cheese (4 oz) oils/butter (2 tbsp)
cream (2 tbsp) mayonnaise (2 tbsp)
Leafy greens (~2 grams of carbs/cup):
arugula endive spinach
bok choy greens (including beet, collards, mustard, and turnip) radicchio
cabbage (all varieties) kale radishes
chard lettuce (all varieties) scallions
chives parsley watercress
Non-starchy vegetables (~5 grams of carbs/cup):
artichokes jicama snow peas
asparagus leeks sprouts (bean & alfalfa)
broccoli mushrooms sugar-snap peas
Brussels sprouts okra summer squash
cauliflower onions, shallots tomatoes
celery peppers wax beans
cucumber pumpkin zucchini
eggplant rhubarb green beans (string beans)
Starchy vegetables/starches (~20 grams of carbs/cup):
grains (even “whole” grains) flour pastas
rice cornstarch muffins
cereals breads bagels
tortillas carrots potatoes
crackers parsnips French fries
slow-cooked beans (pinto, lima, black beans, etc.) corn potato chips
peas tortilla chips
Snack ideas:
hard cheeses olives hard boiled or deviled eggs
nuts pepperoni or salami slices celery with nut butter
Note: Emphasis should be placed on the starches with the lowest glycemic impact.
Comment: Low carb diets include full fat dairy products such as full fat cheeses, cream and sour cream, and full fat plain yogurts. Individuals should be aware of the total carb count in the lactose component of the product and serving size. For example, in coffee, heavy cream is preferred over skim milk.

Figure 1. Reading a Nutrition Facts Label

There are two ways to count carbs: TOTAL CARBS or NET CARBS

Total Carbs
  • Look at the serving size and total carbohydrate sections
  • In this example, 4 grams carbohydrate = 4 total grams of carbohydrate per 1 cup of cauliflower
  • TOTAL CARBS is used when individuals are trying to lose weight most effectively
Net Carbs
  • Look at the serving size, total carbohydrate and dietary fiber sections.
  • Subtract dietary fiber from total carbohydrate to get the “net carbs.”
  • In this example, 4 grams carbohydrate – 2 grams fiber = 2 grams “net carbs” per 1 cup of cauliflower.
  • NET CARBS is more often used for individuals trying to lose weight more gradually or maintain body weight.
  • Packaged or processed low-carbohydrate foods often contain sweeteners called sugar alcohols (e.g., erythritol, maltitol, xylitol, isomalt) that are carbohydrates. Some people think sugar alcohols can be subtracted similar to fiber when calculating “net carbs,” but most of them contain about half the calories per gram that carbohydrates contain.
Individualizing Carbohydrate Intake Level
  • The effective carbohydrate intake level can vary considerably from patient to patient, as can strategies for determining that level.
  • The level depends on several factors including age, gender, metabolic rate, insulin sensitivity, activity level, and quality of carbohydrate (glycemic index/load).
  • One effective strategy is to start at a level that is effective for most everyone, typically ~20 g of total carbohydrate per day. This level achieves weight loss and ketogenesis in most individuals.
  • Then, small amounts of carbohydrate (~5 g) can be added to the daily amount each week in the following situations:
    • As the patient reaches the goal for weight or another goal such as blood glucose control
    • If cravings for carbohydrate might lead the patient to abandon the eating plan
    • If side effects of the eating pattern (e.g., constipation) cannot be managed otherwise and threaten continued adherence.
  • Ideally, 5 g of carbohydrate from one type of food (e.g., ½ cup berries, 1 cup of non-starchy vegetable or 1 oz of nuts) is added daily for 1 week.
  • If weight loss (or weight stability, if that is the goal) continues, then another 5 g of carbohydrate from the same or another type of food can be added.
  • In this manner, the patient can identify a level of carbohydrate intake below which weight loss can be achieved and a higher level at which weight stability can be achieved.

General Eating Principles to Communicate with Patients

  • A low-carbohydrate nutritional approach has a natural appetite reduction effect to ease you comfortably into the consumption of smaller and smaller quantities. Therefore, counting calories is not required.
  • Eat when you are hungry and stop when you are comfortably full.
  • You do not have to eat if you are not hungry. Skipping meals is acceptable as long as you do not overeat or eat high carbohydrate foods later due to delayed hunger.
  • You do not have to eat everything on your plate “just because it’s there.”

Medication Management

Medication Management

Monitoring and Adjusting Medications

  • The most important task for the clinician using low-carbohydrate nutrition therapy is to adjust medications to minimize the risk for hypoglycemia and hypotension. Note: For safety and efficacy, the authors feel it is important for the patient to have daily accessibility with the health care team when adjusting medications so daily adjustments can be made if needed.
  • Reducing carbohydrate intake potently reduces blood glucose level, which means that diabetes medications can be reduced.
    • Particularly insulin and insulin secretagogues (sulfonylureas, meglitinides) can lead to hypoglycemia and therefore usually need to be reduced at onset of dietary change.
  • Reducing carbohydrate intake also leads to water loss, partly from the use of glycogen stores (glycogen is stored with water) and partly from lower insulin levels (insulin, particularly when combined with hyperglycemia, signals the kidneys to retain sodium). As a result, blood pressure can decrease and dehydration can occur if water and sodium are not replenished.
  • Insulin and insulin secretagogues should be adjusted ON THE SAME DAY that the patient is starting the new eating plan using the algorithms as guidance.
  • Frequency of monitoring thereafter should be individualized based on the patient’s comorbid conditions, concomitant medications, health literacy, age and other factors.
  • For patients taking larger doses of insulin or diuretic, clinic visits every 1-2 weeks may be necessary at the beginning, and avenues for communication should be made available if advice is needed between visits.
  • Elevations of blood glucose in the 150-250 mg/dl range can be tolerated after medication reductions are made while patients are adapting to low-carbohydrate nutrition and losing weight—this gives a “buffer” from hypoglycemic episodes.
  • As weight loss continues, blood glucose levels will decline and further medication reductions may be necessary.
  • Visits can be spaced out to monthly when blood glucose or blood pressure is at goal with no or rare hypoglycemia or hypotension episodes. Visits can be spaced further, if desired, when weight loss slows to 1-2 lbs. or less per week.

Table 3. Blood Pressure Medication Adjustment

Having trouble viewing table?

Blood pressure, mm Hg Change in one medication
Systolic Diastolic
<110 NA Decrease by 25–50%
110–149 <95 No change
150–169 95–110 Increase by 25–50%
  • For patients with controlled blood pressure and/or controlled edema, consider stopping low-dose or reducing high-dose diuretic medication during first 2–4 weeks to minimize risk for dehydration. Return to prior dose if BP elevates above goal and/or edema recurs.
  • Treat symptomatic hypotension (extreme fatigue) or orthostatic hypotension (dizzy or lightheaded when going from lying/sitting to standing) similar to SBP <110 mm Hg.
  • If reducing medication already at minimum dose, stop that medication.
  • If increasing medication already at maximum dose, add one medication at starting dose.
  • Follow diabetes/coronary artery disease/congestive heart failure guidelines regarding choice of agents when starting or stopping medication.

Figure 2. Initial Diabetes Medication Changes

Figure 3. Follow-Up Diabetes Medication Changes

Table 4. Adapting Diabetes Medication for Low Carbohydrate Management of Type 2 Diabetes

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Drug Group Action Hypoglycemia risk? Clinical suggestion
Biguanides (metformin) Reduce hepatic gluconeogenesis. Reduce peripheral insulin. No Optional, consider clinical pros/cons.
GLP-1 agonists Slow gastric emptying. Increase satiety. Increase insulin secretion. No Optional, consider clinical pros/cons.
Insulins Exogenous insulin. Yes Reduce/Stopa
Sulfonylureas Increase pancreatic insulin secretion. Yes Stop (if gradual carbohydrate reduction then wean by halving dose)
Meglitinides Increase pancreatic insulin secretion. No Reduce/Stop (if gradual carbohydrate reduction then wean by halving)
SGLT-2 inhibitors Reduce renal glucose reabsorption, increasing glucose excretion in the urine. No Consider stopping, especially with significant carbohydrate restriction. (SGTL2i’s may cause ketoacidosis, including with euglycaemia)
Thiazolidinediones Reduce peripheral insulin resistance. No Usually stop, concerns over long term risks usually outweigh benefit.
DPP-4 inhibitors Inhibit DPP-4 enzyme, potentiating GLP-1 effect. No Usually stop, due to lack of benefit.
Alpha-glucosidase inhibitors Delay digestion of starch and sucrose. No Usually stop, due to no benefit if low starch/sucrose ingestion.
Self-monitoring blood glucose Provide feedback on blood glucose and response to food. N/A Important to be available for people on drugs that risk hypoglycaemia. May be useful also for helping to understand blood glucose response.
a Insulin reduction suggestion: Important to tailor to individual. Usually requires close supervision with healthcare professional, and if in doubt seek expert input.
T2DM without ‘beta cell failure’: Usually reduce insulin dosage by approximately 50% (though a 30% initial reduction may be appropriate for those with a high HbA1c). Monitor for hypoglycemia, with rescue glucose if required. Continue down-titration of insulin as insulin resistance improves (can take months in some cases). Goal for most can be to eliminate exogenous insulin.
Caution: Some people diagnosed with T2DM may have significant ‘beta cell failure.' Also people with other forms of pancreatic insufficiency (e.g. LADA) may have been misdiagnosed as T2DM. Consider these possibilities if patient was not overweight at diagnosis. Inappropriate over-reduction and cessation of exogenous insulin is avoidable in these cases as they will become hyperglycemic.
Adapted from: Br J of GP July 2019 ; Murdoch C, Unwin D, Cucuzzella M, Patel M, Cavan D

Maintenance and Adherence

Maintenance and Adherence

Table 5. How to Manage/Prevent Potential Side Effects

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Potential Negative Effects Prevention/Management Solution
Transient symptoms such as headache, fatigue, lightheadedness or diarrhea, commonly called the “keto flu.” If uncontrolled hypertension or heart failure is not present, adding fluid and sodium (e.g., bouillon 1–2 cubes/day) can prevent or reduce these symptoms. These symptoms typically resolve in 7–10 days. As with viral flu, patients should rest and avoid heavy exertion during this initial stage of the nutrition plan if symptoms occur.
Halitosis Increase water intake, maintain good oral hygiene and use parsley, sugarless mints or chewing gum. In some cases, modification of macronutrient intake may be helpful.
Large increases in LDL If LDL cholesterol increases more markedly, this can be managed by focusing on intake of plant-based foods (non-starchy vegetable consumption), leaner protein sources and increased unsaturated fats while reducing foods high in saturated fat (e.g., full-fat dairy products like butter, cream and cheese; processed meats; poultry skin).
Constipation To prevent constipation, providers should emphasize non-starchy vegetables high in insoluble fiber, adequate fluid intake with the majority as water, and regular weight-bearing physical activity. If constipation occurs, stool softeners such as docusate should be the first line choice for treatment, followed by osmotic laxatives (See Table 6). Stimulant laxatives should not be used regularly due to potential risk of bowel hypotonia and dependency.
Hypoglycemia Lowering carbohydrate intake should not cause hypoglycemia unless there is concomitant use of insulin or insulin secretagogues.

Table 6. Summary of Common Osmotic Laxatives

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Type Generic Name Dosage Side Effects/Problemsa Mechanism of Action
OTC Products
Hyperosmolar agents Sorbitol 15–30 mL daily or bid Sweet taste, transient abdominal cramps, flatulence, bloating Nonabsorbable disaccharides metabolized by colonic bacteria into acetic and short-chain fatty acids, which accelerate colonic transit
Lactulose 15–30 mL daily or bid
Polyethylene glycol 17 g/d Incontinence due to potency, bloating, abdominal cramps Osmotically ↑ intraluminal fluids
Saline laxative Magnesium 15–30 mL daily or bid Magnesium toxicity, dehydration, abdominal cramps, incontinence Fluid osmotically drawn into small-bowel lumen, cholecystokinin stimulated, colon transit time ↓
Magnesium citrate 5–10 fl oz (150–300 mL) once Avoid in renal failure
a Potentially all laxatives and constipation treatments may cause fecal incontinence.

Physician-Patient Communication Topics — Dispelling Myths

  • Myth: Low-carb nutritional approaches are a fad
    Response: Over the past several decades, many randomized controlled trials, both short term and long term (up to 2 years or more), have demonstrated that a low-carbohydrate eating pattern is effective for weight loss, metabolic improvement, and weight maintenance.
  • Myth: Low-carb is bad for your heart
    Response: Carefully controlled randomized trials have demonstrated reduction in cardiometabolic risk factors and carotid intimal thickness.
  • Myth: Low-carb is not sustainable long-term
    Response: Reducing daily carbohydrate intake has the effect of decreasing appetite and increasing satiation or sense of fullness and corresponding biomarkers. This effect assists in long term maintenance. Randomized trials typically show that patients persist with low-carbohydrate eating plans similarly to comparison diets.
  • Myth: Plant foods are reduced
    Response: Non-starchy vegetables (green leafy, cruciferous, zucchini, cucumber, celery, etc.) are the foundational foods of a low-carbohydrate eating pattern and are nutrient dense with abundant amounts of folate, potassium, vitamins and phytonutrients. Proteins or fats can also be obtained from vegetable sources such as nuts, tofu, tempeh, olive oil, avocado and others.
  • Myth: Ketosis is dangerous because the brain needs glucose
    Response: Restricting dietary carbohydrates has been an established treatment option for children with hard to control epilepsy since the 1920s and has no proven deleterious effect on cognitive function.
  • Myth: Ketone products and fats are necessary to get into nutritional ketosis
    Response: The most important factor to attain nutritional ketosis is to consume a small amount of carbohydrate. Adding ketones or fats or oils is not necessary.
  • Myth: Low-carb eating patterns negatively influence kidney function
    Response: This myth stems from the confusion between low-carb eating patterns and high-protein eating patterns. Low-carb does not necessarily mean high protein. Further, for people without existing kidney disease, and for those eating to satiety, higher protein intake does not appear to be related to lower kidney function.

How to Increase Maintenance

  • Long-term sustainability may be improved by behavioral analogies like budgeting. Expectation is not avoidance of all carbohydrates but specific choices of foods low in digestible carbohydrate.
  • Cravings for carbohydrate-rich foods are common, and unplanned deviations from any dietary pattern or lifestyle plan are normal and to be expected. Counseling emphasis should be placed on returning to the prescribed eating pattern and developing plans to remove, avoid or respond differently to triggers.
  • Discussing in plain language “binge management strategies” and “emotional management strategies” initially and periodically is essential.
  • Vegetarian dietary patterns, even vegan patterns, can be adapted to a low-carbohydrate goal with the inclusion of vegetable products which are high in protein content — e.g., soybeans, tofu, tempeh, and vegetable fats such as avocados, olives, nuts, seeds and nut butters.

Recommendation Grading


  • ACE: Angiotensin-converting Enzyme
  • ARB: Angiotensin Receptor Blocker
  • ASCVD: Atherosclerotic Cardiovascular Disease
  • BID: Two Times A Day
  • BP: Blood Pressure
  • CAC: Coronary Artery Calcium
  • CBC: Complete Blood Cell Count
  • CGM: Continuous Glucose Monitoring
  • CMP: Complete Metabolic Panel
  • CVD: Cardiovascular Disease
  • GLP-1: Glucagon-like Peptide-1
  • GTT: Glucose Tolerance Test
  • HDL: High Density Lipoprotein
  • HbA1C: Hemoglobin A1C
  • LADA: Latent Autoimmune Diabetes In Adults
  • LDL: Low Density Lipoprotein
  • OTC: Over The Counter
  • SBP: Systolic Blood Pressure
  • SGLT-2: Sodium-glucose Co-transporter-2
  • TC: Total Cholesterol
  • TG/HDL: Triglyceride To HDL
  • hsCRP: High-sensitivity C-reactive Protein


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