Frequently Asked Questions

“Low carbohydrate” is not defined by the U.S. Food and Drug Administration, and the definition of a low-carbohydrate diet varies in the literature. However, most experts in the field agree that a low-carbohydrate diet should be limited to a maximum of 130-150 g/day (1), and many experts consider the cut-off of 130 grams/day as it is below the Adequate Intake set by the IOM. In fact, a strong body of research shows limiting intake to no more than 130 grams/day, or less than ~25% of total daily calories, promotes a variety of positive metabolic outcomes (2).
An amount of less than 50 g of carbohydrate per day is considered very low carbohydrate, which would put most adults into nutritional ketosis (3). During this state, the body relies primarily on fatty acids and ketone bodies produced from fat stores, not glucose, for energy.

Mounting evidence has demonstrated that restricting carbohydrate intake is associated with wide-ranging benefits.

• Weight Loss: LCDs enable the body to preferentially metabolize fat for energy. Carbohydrates are the major stimuli for insulin release, which, in turn, inhibits fat breakdown, promotes fat storage, and complicates weight-loss efforts. Reducing carbohydrate intakes, and consequently insulin levels, results in a unique metabolic state—lipolysis and ketosis—enabling the body to increase fat oxidation for energy use and decrease fat synthesis (5, 6, 7), resulting in total body fat reduction and, thus, weight loss.
• Chronic Disease Prevention and Management: Beyond weight loss, studies also show carbohydrate restriction results in global improvements in biomarkers related to metabolic syndrome, cardiovascular disease, and diabetes. Evidence consistently shows LCDs help reduce hemoglobin A1c and blood pressure, improve lipoprotein profiles, and increase resting and total energy expenditure values (9, 10, 11, 12).

Importantly, evidence from multiple studies indicate that, for most people, restricting carbohydrates is also a more effective dietary intervention than restricting dietary fat (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29). This is supported by a systematic review and meta-analysis concluding that low carbohydrate diets have favorable effects on weight loss, metabolic syndrome, and major cardiovascular risk factors (30).

Ketosis (aka: “nutritional ketosis”) is a completely natural physiological adaptation that is integrated into the body’s energy strategy whenever carbohydrates are limited, and fat becomes its primary fuel. When this occurs, the liver forms ketones – more specifically acetoacetate (AcAc) and hydroxybutyrate (BOHB) – which enable fatty acids from adipose tissue to be used for energy. Interestingly, beyond safe and effective weight loss, research also suggests that the ketone BOHB may play an epigenetic role in reducing oxidative stress and inflammation (31).

Ketoacidosis is characterized by dangerously high levels of ketones (>10 mmol/L), a roughly 10-fold increase from ketone levels achieved by nutrition ketosis. Ketoacidosis is rare and typically only occurs in people with uncontrolled type 1 diabetes.

Atkins 20 and Atkins 40 are examples of ketogenic diets, which raise ketone levels to 0.5-3 mmol/L—this range is often described as nutritional ketosis when excess ketones are excreted in the urine, breath, and skin (32).

The Atkins Nutritional Approach is built on science and designed for life.

One of the unique things about the Atkins diet is that the program reintroduces carbohydrates as patients lose weight and/or improve their glycemic tolerance. This approach is supported through years of practical experience, which has shown that variety is important for compliance. Furthermore, this is the approach that has been demonstrated to be successful in many randomized control trials of low carbohydrate diets (33, 34, 35).

Moreover, today’s Atkins Nutritional Approach is intended to provide the support and flexibility needed for a lifetime of healthy behaviors, not just short-term weight loss. Rather than providing all-or-nothing rules, it offers an adaptable and individualized road map across three program options – Atkins 20, Atkins 40, and Atkins 100. Each plan is designed around different intakes of “net carbs”, total carbohydrates minus fiber in whole foods.

• Atkins 20 allows people to follow a structured approach to reduce overall net carbohydrate intake. In Phase 1, net carbs are limited to 20-25 grams/day until the patient is within 15 pounds of goal weight. Net carbs are then liberalized to 25-50 grams/day in Phase 2, which typically lasts until the patient is within 10 pounds of his/her goal weight. Net carbs are increased to 50-80 grams/day in Phase 3 until goal weight is achieved, and finally to 80-100 grams/day in Phase 4 – “Lifetime Maintenance.” This ketogenic plan is ideal for those looking to lose 40 pounds or more.
• Atkins 40 begins with a slightly higher baseline net carb intake of 40 grams/day. As the individual approaches his/her weight-loss goals, net carb amounts are gradually liberalized by 10 grams of net carbs/week until goal weight maintenance is achieved. This ketogenic plan is ideal for those looking to lose fewer than 40 pounds.
• Atkins 100 is a low carbohydrate diet focused on consuming 100 grams of net carbs/day. It is a flexible yet carbohydrate-conscious approach to a long-term, healthy lifestyle. While not technically a ketogenic plan, the net carb level achieved with Atkins 100 is ideal for those looking to maintain their weight and achieve long-term health goals.

While program phases are designed to be progressively liberal, clinicians may encourage patients to go at their own pace. Carbohydrate tolerance levels are personalized; there is no one-size-fits-all approach to the lifetime maintenance. Individuals may choose to start their process at a later phase and move forward or backward in whatever way feels most manageable and best meets their needs. Plans can also be adjusted to honor individual patients’ food preferences, culinary traditions, and fitness choices.

In a 2019 consensus report, the American Diabetes Association (ADA) affirmed that reducing overall carbohydrate intake has demonstrated the most evidence for improving glycemia in people with type 2 diabetes, and low- or very low-carbohydrate eating plans, like the Atkins Diet, are a viable approach for adults with type 2 diabetes who are not meeting glycemic targets, or for whom reducing anti-glycemic medications is a priority. In their 2020 guidelines, the ADA went as far as stating, “Reducing overall carbohydrate intake for individuals with diabetes has demonstrated the most evidence for improving glycemia and may be applied in a variety of eating patterns that meet individual needs and preferences (36).”

Additionally, multiple well controlled studies have demonstrated that low-carbohydrate diets (like Atkins Diet) can be extremely beneficial for people with T2D.

In a study by Hussain, et al. (37), 363 people diagnosed with pre-diabetes or diabetes were offered either a standard low-fat diet, a low-calorie diet or a ketogenic diet, similar to Atkins. After 6 months, weight loss and blood lipid changes were significantly better with the Atkins-type diet compared to the standard diet. And, among people with diabetes on the ketogenic diet, both HbA1c and fasting glucose were reduced to near-normal levels, with concurrent reductions in diabetes medications. Similar results have been reported by Boden et al (38), Bistrian et al (39), Dashti et al (40), all demonstrating that carbohydrate restriction can improve glucose control, reduce serum insulin levels, and reduce or obviate medication requirements in patients with type 2 diabetes. For more information on to put this into practice, please visit the Atkins resource: Low-Carbohydrate Nutrition Approaches in Patients with Obesity, Prediabetes and Type 2 Diabetes.

A growing body of literature demonstrates that complying with a low-carbohydrate diet (LCD), like the Atkins Nutritional Approach, reduces risk factors for CVD and improves related biomarkers. In fact, contrary to longstanding beliefs, studies increasingly show that an LCD can be more effective in reducing CVD risk factors than a low-fat dietary pattern (41). The reduced conversion of carbohydrate to fat in the liver (lipogenesis), plus the low insulin state enabling accelerated fat oxidation, are major factors contributing to the lipoprotein improvements commonly observed in patients following the Atkins Diet. CVD biomarker improvements may include:

• Decreased Triglycerides: The most consistent response to an LCD intervention is a sharp decrease in plasma triglycerides, most dramatically in those with pre-existing hypertriglyceridemia (7).
• Increased HDL: The increase in HDL may not occur as quickly as the decrease in triglyceride, but, based on empirical evidence, this slowly developing HDL boost appears to persist long-term even as carbohydrate intake gradually increases (22).
• Improved LDL Patterns: LCDs increase the prevalence of larger LDL particles, whereas low fat/high carbohydrate diets have the opposite effect. This inverse relationship between dietary carbohydrate content and LDL particle size has been observed over a wide range of carbohydrate intakes (42), and it can have quite dramatic effects at very low carbohydrate consumption levels, as those recommended by the Atkins Diet (12). The more carbohydrate intake is decreased, the more LDL distribution shifts from ‘pattern B’ LDL, characterized by predominantly small LDL particles, to the preferential ‘pattern A’, characterized by a larger proportion of large particles. A growing body of research suggests these LDL patterns may be a better indicator of CVD risk than overall LDL counts.

The Atkins Diet promotes both short- and long-term physiological changes and biomarker improvements; reducing or discontinuing some medications can be expected. It is recommended that people have daily accessibility to a healthcare team to allow for titrations, as warranted. Two common adjustments often needed include:

• Reducing Diabetes Medications: Insulin and insulin secretagogues (sulfonylureas, melitinides) are particularly apt to lead to hypoglycemia and typically need to be reduced. These medications typically need to be adjusted on the same day the patient begins the Atkins Diet. Moderately elevated blood glucose levels in the 150-250 mg/dl range can be tolerated after medication reductions are made and as patients are adapting to the new eating pattern – this may “buffer” hypoglycemic episodes. As weight loss continues and glycemic control improves, further medication reductions may be necessary.
• Adjusting Diuretics: Reducing dietary carbohydrates has a diuretic effect. This is partly a result of the breakdown of stored glycogen, which is bound to water, and partly due to decreased insulin levels, which signals the release of sodium and water from the kidneys. For patients with controlled blood pressure and/or controlled edema, the clinician may consider stopping low-dose or reducing high-dose diuretics during the first 2–4 weeks to minimize dehydration risk. Return to the prior dose if blood pressure elevates above goal and/or edema recurs.

Learn more about medication management guidelines in the Atkins resource: Low-Carbohydrate Nutrition Approaches in Patients with Obesity, Prediabetes and Type 2 Diabetes.

The Atkins Nutritional Approach recommends an intake of about 12-18 ounces of protein foods per day, (4 to 6 ounce serving per meal) an amount typically under 30% of total daily calories for any given individual and considered safe by major health organizations. Though this intake is slightly higher than the recommended dietary allowances (RDA) for protein, it’s important to understand that RDA represents the minimum level considered sufficient to meet the requirements of most people within a healthy population. It is not intended to represent an upper limit or even an optimal intake amount (43). In fact, downshifting carbohydrate intake while consuming a moderate-protein and higher-fat diet, as achieved through the Atkins Nutritional Approach, has been shown to promote satiety and drive sustainable weight loss (44, 45, 46).

The Atkins Nutritional Approach offers flexibility and personalization to meet the needs of practically any individual and makes room for plenty of plant-based options.

• For vegetarian patients, help guide them toward conscientious protein choices that include eggs, dairy, and high-protein plant foods (e.g., soy, beans, lentils, nuts, whole grains, etc.) in order to meet their protein needs. Encourage these patients to start Atkins 20 in Phase 2 at 30 grams of net carbohydrates/day. This small adjustment helps ensure they get enough protein from non-meat sources from the start.
• For vegan patients, protein options are further limited to plant-based foods only. To honor these dietary restrictions, encourage these patients to start Atkins 20 in Phase 2 at 50 grams of net carbohydrates/day. Similar to the vegetarian plan, this adjustment helps make space for adequate protein from plant-based sources at the outset. Additional considerations may be made regarding protein and/or micronutrient dietary supplements.

While the Atkins Nutritional Approach does provide the flexibility to follow vegetarian and vegan eating patterns, it will likely result in a slower rate of weight loss. However, long-term weight loss and overall health improvements can still be achieved.

In line with post-bariatric guidelines, the Atkins Nutritional Approach promotes portion control; encourages consumption of protein- and micronutrient- foods; and limits sugar, concentrated sweets and certain starchy foods. Additional post-bariatric diet recommendations (e.g., fluid guidelines, caffeine and alcohol restrictions, supplement regimens, etc.) are compatible with the Atkins program. HCPs should provide additional guidance, structure, and support for patients struggling with diet adherence or weight regain. Before recommending the Atkins Nutritional Approach, the clinician must consider each individual patient’s needs, challenges, preferences and readiness.

As with any lifestyle change, beginning the Atkins Diet may feel confusing, uncomfortable, or even challenging for patients. Proactive prevention and timely management of potential negative effects of starting a new diet is key. Common patient concerns, include:

• Electrolyte Imbalance: Ketosis has a diuretic effect and electrolyte disturbances may occur (this also accounts for the flu-like symptoms described below). Both sodium and potassium can be an issue, and while sodium can be supplemented with broth, potassium is more difficult to come by. Consider recommending more low-carbohydrate, potassium-rich foods (e.g., avocados and dark leafy greens) or prescribing a dietary supplement.
• Flu-like Symptoms: Transient symptoms like headache, fatigue, lightheadedness, or diarrhea (aka, “keto flu”) are not uncommon in the initial days of adaptation and typically resolves in 7-10 days. If hypertension or heart failure is not present in your patient, consider adding fluid and a modem of sodium to their daily diet to prevent or minimize these experiences. As with viral flu, patients should rest and avoid heavy exertion if these symptoms occur.
• Halitosis: Though a bit embarrassing, “keto breath” is an encouraging sign that fat loss has begun. Encourage patients to drink more water, maintain good oral hygiene, and use sugar-free breath fresheners like sugarless mints, chewing gum, or parsley. In some cases, macronutrient modification (i.e., decreasing protein and increasing fat) may be helpful. This usually resolves itself after the adaptation phase.
• Constipation: As intake of fruits, whole grains, and starchy fibrous vegetables is curtailed, constipation may result. Emphasizing non-starchy vegetables high in insoluble fiber (e.g., Brussels sprouts, broccoli, carrots etc.), adequate water intake, and regular weight-bearing exercise can help patients avoid this uncomfortable side effect. If constipation does occur, stool softeners should be the first line of defense, followed by osmotic laxatives. Stimulant laxatives should not be used regularly due to potential risk of bowel hypotonia and dependency.
• Hypoglycemia: It is important for patients to know that lowering carbohydrate intake is not expected to trigger a hypoglycemic episode when concomitant insulin secretagogues have been discontinued. Equally important, patients should understand that responding appropriately to signs of hypoglycemia, should they occur, is more critical for their immediate well-being than that day’s adherence to their low-carbohydrate eating plan.

For more information on how to manage or prevent potential side effects, see Low-Carbohydrate Nutrition Approaches in Patients with Obesity, Prediabetes and Type 2 Diabetes.

Active listening, accessibility, and non-judgmental support can go a long way in helping others overcome barriers to long-term behavior change. When providing patient counseling, keep the following strategies in mind:

• Reinforce the concept of purposeful permission. The expectation is not avoidance of all carbohydrates. Instead, it’s about making purposeful carbohydrate choices (i.e., those low in net-carbohydrates and high in nutrition) most of the time.
• Frame setbacks as learning opportunities. Nobody is perfect. Unplanned deviations from the meal plan are normal and to be expected. Approach these moments with compassion; help your patients focus on returning to the prescribed eating pattern without ‘self-punishment,’ and work with them to develop strategies to remove, avoid, or respond differently to triggers.
• Acknowledge disordered and emotional eating strategies. Often, people are not forthcoming about binge eating or compulsive eating behaviors, yet these issues are not uncommon and may underlie weight gain and related health problems. Destigmatize these behaviors from the start, counsel patients on behavior management strategies and reach out for expert support, when needed. The National Eating Disorders Associationis a good place to start if you’re looking for more information or seeking referral information.
• Be your patient’s navigational system. The Atkins Diet provides a roadmap and the clinician holds the compass. If motivation or self-efficacy are low, recommend beginning the program at a more liberal, “later” phase. If dietary control and consistency are wavering, have patients double-back to the start for greater structure and support. “Alternative routes” are available to meet individual food preferences or dietary needs. The Atkins Nutritional Approach helps guide the way, but having a healthcare professional “copilot” is crucial to navigate detours and roadblocks.