The ketogenic (keto) and Atkins diets are two low-carbohydrate eating plans used by some people for weight management and metabolic changes. There may be short-term benefits, but research on long-term health effects is mixed and may include cardiometabolic risk and nutrient deficiencies.
The recommended daily intake of carbohydrates for adults is about
This article looks at the similarities and differences between the keto and Atkins diets, including their potential benefits and adverse effects and the foods involved.
The keto and Atkins diets both aim to promote weight loss and improve health by limiting carb intake.
Both diets significantly limit carbs such as grains and sugars. The keto diet is typically more restrictive of overall carbohydrates than the Atkins diet.
The keto diet puts more emphasis on eating healthful fats than the Atkins diet.
Understanding how these diets work can help a person decide whether either is a good choice.
The keto diet
A person following the keto diet will eat very few carbohydrates, lots of fat, and some protein.
Below are the proportions of a person’s total daily macronutrient intake on the keto diet:
- 70–80% fat
- 20–25% protein
- 5–10% carbohydrates
Carbs are the body’s go-to source of fuel. The keto diet involves significantly reducing levels of carbs so that the body can no longer use them for fuel.
When carbohydrate intake is very low, the body may enter ketosis. Ketosis is a metabolic state where ketones replace glucose as a fuel source. Although ketosis can promote short-term fat loss, it is not inherently beneficial for everyone and may carry metabolic risks over the long term.
Keto diet proponents recommend getting the carbs allowed from specific foods, including keto-friendly vegetables, such as leafy greens, and certain fruits, primarily berries. The diet excludes grains and legumes.
The Atkins diet
Like the keto diet, the Atkins diet allows for few carbs, moderate amounts of protein, and high amounts of fat.
Over the years, the Atkins diet has evolved to include various eating plans. The current name for the original version of the diet is “Atkins 20.”
According to the Atkins website, this diet consists of 4 phases distinguished by the amount of carbs that a person eats each day:
- Phase 1 – This is the most restrictive phase, allowing for just 20–25 g of carbohydrates per day. People stay in this phase until they are 15 pounds from their ideal weight.
- Phase 2 – During this phase, people eat 25–50 g of carbs each day.
- Phase 3 – This allows people to eat up to 80 g of carbs per day until they meet their goal weight and maintain it for at least 1 month.
- Phase 4 – Phase 4 is the maintenance phase, allowing for 80–100 g of carbs per day.
The final phase is the least restrictive. The aim is to help a person be conscious of their carb intake and maintain a healthful weight.
During the first phase, the body enters ketosis, as in the keto diet. As the person moves through the different phases, they begin to eat more carbs and more varied foods.
The keto and Atkins diets both involve restricting carb intake, even in the final phase of the Atkins diet. However, there are key differences.
Restriction
In general, the keto diet is much more restrictive than the Atkins diet.
The keto diet places more emphasis on carb elimination, and it restricts protein sources, as the body may break down proteins into glucose for energy. The vast majority of calories in the keto diet come from fat.
The Atkins diet places strong restrictions on carbohydrate intake at first, but it allows for moderate protein intake. As the person moves through the stages, the Atkins diet becomes more relaxed, allowing for more carbs and a greater variety of foods.
Ketosis
The keto and Atkins diets can both lead to a state of ketosis.
However, in the Atkins diet, only the first — and sometimes second — stages involve the carb restriction required to maintain ketosis.
If a person follows it strictly, the keto diet involves continuous ketosis.
Long-term viability
Long-term evidence on safety and healthfulness of very-low-carbohydrate diets remains limited. Some observational studies have linked high animal-protein, high-fat, low-carb plans with increased mortality and cardiometabolic risk, especially when saturated fats are predominant.
Another 2019 systemic meta-analysis found that low carbohydrate diets were associated with increased mortality. When carbohydrates were replaced by animal fats and proteins, mortality increased. Plant-based replacements were linked to lower mortality.
Some people find that the Atkins diet is an achievable long term option. Though it starts restrictive, a person introduces more foods and carbs as they get close to their goal weight.
The last stage, or maintenance stage, of the Atkins diet can feel more manageable than keeping up with the perpetually restrictive keto diet.
However, it is dangerous to remain in ketosis for extended periods. Also, most people are unable to maintain a very high fat intake or extreme carb restriction for a long time.
Origins
Doctors
Dr. Robert Atkins developed the Atkins diet as a simple, low carbohydrate approach to nutrition. The diet has changed over the years to take on its four stage structure.
Both the Atkins and keto diets involve carb restriction, and the effects can be similar.
Weight loss
Many people follow the keto or Atkins diets for weight loss.
A number of studies have shown that these diets can result in weight loss, as the body burns fat very well when it enters ketosis. Short-term weight loss can occur with low-carbohydrate diets, but long-term outcomes often converge with other balanced diets. Dietary adherence and food quality strongly influence results.
As this 2025 article notes, ketosis may help manage obesity and metabolic risk factors that are precursors to type 2 diabetes. However, confirming these findings will require more research.
Potential health benefits
Recent
Recent meta-analyses show that ketogenic or very low-carbohydrate diets consistently improve some metabolic markers, including:
- Triglycerides and HDL:
Research reports decreased triglycerides and increased HDL cholesterol with ketogenic diets compared with control diets. - Blood glucose and insulin resistance: A large meta-analysis found that very low-carbohydrate ketogenic diets significantly reduced fasting blood sugar, HbA1c, and HOMA-IR, which is an insulin resistance measure.
There is emerging evidence these diets may help with other issues, such as acne and neurological disorders, although confirming this will require more research.
Focus on natural foods
Both diets encourage a person to eat unprocessed foods. Highly processed foods are linked with obesity, cardiovascular disease, and other health conditions.
Side effects and risks
Ketosis and extended very-low-carb regimens are associated with side effects ranging from keto flu to nutrient and electrolyte imbalances. Side effects can include keto breath, keto skin rashes, and keto flu. Long-term impacts, including effects on liver function, microbiome diversity, and cardiovascular risk, require more study.
Also, people following either diet can develop nutrient deficiencies due to food restrictions. For many people, carbohydrate sources are also key sources of fiber. When reducing carbohydrates, people should be sure to get enough daily fiber from other sources, such as vegetables.
In addition, these diets may increase the risk of deficiencies in electrolytes and many water-soluble nutrients that come from fruits and vegetables.
Finally, ketosis may help burn fat, but it may also burn muscle to use for energy. Following a very low carb diet can result in a loss of muscle mass.
There are many similarities to the keto and Atkins diets. Both require a significant reduction in calories from carbohydrates and encourage a person to get their calories from fats.
The keto diet puts greater restrictions on the source of calories. The Atkins diet starts very restrictive but becomes less so over time, allowing a person to eat a greater variety of foods.
Restrictive diets may help with short term weight loss or fitness goals, but they may not be as healthful in the long term as other options.
Consult a clinician or registered dietitian before making any major dietary change. This is especially important for people with chronic health conditions, such as heart disease, diabetes, high blood pressure, or eating-related concerns.
Consider cultural food preferences, food access, and personal health goals as you make decisions.
When following any diet that eliminates food groups, make sure to avoid deficiencies by meeting daily nutrient needs in other ways.
Once a person reaches their target weight goals, it may be a good idea to switch to a less restrictive diet that incorporates a variety of nutrient-rich foods. Getting the right amount of daily physical activity can also help with maintaining a healthful weight.