At one time, low-carbohydrate diets were dismissed as fad diets. Their claims for producing quick, significant weight loss were dismissed as being grossly exaggerated as well as being unhealthy and unsustainable (1). Even without the assistance of spin doctors or far-reaching marketing campaigns, the reputation of low-carb diets has evolved (2). The transition has been more of an organic, grass-roots movement than a well-orchestrated advertising campaign. Watching as their friends steadily drop pound after pound, onlookers eventually ask, “How did you do it?”
The term “low-carb” refers to diets that restrict the intake of carbohydrates to some degree, while at the same time increasing the consumption of protein and various fats (3). These three classes of nutrients—carbs, protein, and fat—encompass the principal sources of food calories. As we shall see, however, not all food calories are metabolically equivalent. Many popular diets fall within the low-carb spectrum. While they share some of the same guidelines, they also vary widely.
Note: It is important to remember that changes in diet can be hazardous for some individuals, so make sure to check with your healthcare provider before trying any new plan of eating. And, of course, I am neither a physician nor a dietician, so nothing in this article should be interpreted as medical or nutritional advice.
With these caveats in mind, let’s begin our exploration and comparison of three well-known low-carb diets: Paleo, Atkins, and Keto.
The idea behind the Paleo diet is to eat only the things it is claimed our Paleolithic hunter-gatherer ancestors would have eaten (4). In its simplest terms the Paleo diet can be summed up as follows: 1) eat all the lean meats, fish, seafood, fruits and vegetables you wish 2) do not eat any cereals, legumes, dairy products, or processed foods. This is probably not precisely what our svelte stone-age forebears foraged for, but it is certainly much closer to a true Paleolithic diet than what most people eat today.
The Keto Diet is a very low-carb, moderate-protein, high-fat diet. The theory behind this plan is that once starved of sugars derived from carbs and excess protein, the body will use fats for fuel. The metabolic pathways that burn fats instead of carbohydrates produce waste products called ketone bodies, hence the term ketogenic. As a guideline, one might shoot for getting approximately 5% of their total caloric intake from carbs, 15-20% from protein and the remainder from fat.
The Atkins diet is named after its creator, Robert C Atkins, M.D. This diet may be most well-known for advocating unlimited consumption of bacon and cheese. While that may have been the case at one time, the updated version suggests there is no need to avoid saturated fats (3), the kind of fat that is found in meats and cheeses, but also advises they not be overconsumed. In the first phase of the diet, Atkins recommends restricting carbs to 20 grams per day (12-15 grams of those carbs coming from salad greens and vegetables) while eating liberal amounts of protein and fat (5). This initial restriction of carbohydrate intake also induces ketogenisis, but the Atkins plan differs substantially from other fat-burning diets, so it is generally considered to be distinct from the classic keto diet.
Now let’s dig a little deeper into what separates these three low-carb diets.
DISTRIBUTION OF CARBS, PROTEIN, AND FAT
Essentially all foods are made up of a combination of three components: carbohydrates, protein, and fat. All low-carb diets restrict the portion of carbs allowed to one degree or another. The level of restriction and the varying distribution of the remaining components (protein and fat) is where low-carb diets begin to distinguish themselves (6).
Paleo: The Paleo diet is not based on counting carbs per se. By allowing for the inclusion of liberal amounts of fruit, nuts, and vegetables, the Paleo diet allows for the largest amount of carbs amongst low-carb diets. Paleo is still considered a low-carb diet because even with the allowance of unlimited amounts of fruits and vegetables, total carb consumption is still typically less than that of traditional low-fat diets even though it may be as much as 100-200 grams of carbs daily.
Keto: The basis of the Ketogenic diet is to keep carb intake low enough to get into and remain in ketosis (the state where the body is burning fat and therefore producing ketone bodies). This will vary by person, but generally somewhere between 10 and 50 grams of carbs per day, with some athletes being able to consume up to 100 grams and remain in ketosis. The Keto diet also restrict the amount of protein to a moderate amount claiming that excess protein is not stored in the body but also converted to sugar. Therefore, the Keto diet encourages the consumption of fat, particularly saturated fats such as MCT oil, coconut oil, and animal fat (3).
Atkins: The Atkins diet focuses mainly on the restriction of carbs leaving the proportion of fats and protein consumed up to the discretion of the dieter. The Atkins diet restricts carbs to 20 grams per day for the first two weeks. In subsequent weeks carbs are increased by 5 grams per day until weight loss stalls. At that point, it’s recommended that carbs be reduced by 5 grams per day. It is at that level, typically 40-60 grams daily, that one would stay for the majority of their remaining weight loss journey.
Keep in mind, that on all low-carb diets, the consumption of vegetables is encouraged and there is ample room to consume plenty of vegetables on even the most restrictive low-carb diet. A diet allowing 20 grams of carbs per day, permits the eating of two cups of spinach, one cup butter lettuce, one cup broccoli, one cup zucchini, a medium cucumber, one cup mushrooms, one cup cherry tomatoes, and one cup cauliflower with carbs to spare. It should be noted, that low-carb diets typically count net carbs, not total carbs. Net carbs are calculated by taking the number of total carbs (expressed in grams) and subtracting the number of grams of fiber. For example: one cup of cherry tomatoes contains 6 grams of total carbohydrates and 2 grams of dietary fiber resulting in 4 grams of net carbs (6 gr total carbs – 2 gr dietary fiber = 4 grams of net carbs).
ARTIFICIAL AND NATURAL SWEETENERS
Keeping blood sugar low is one of the benefits of a low-carb diet (7). Low blood sugar levels have the added benefit of reducing cravings.
Paleo: Sweeteners of the any kind are discourage from the Paleo diet although diet sodas are allowed with the disclaimer that aspartame and saccharine may be harmful.
Keto: Natural sweeteners that are low on the Glycemic Index are allowed on the keto diet. These included such sweeteners as Stevia, erythritol, Monk fruit, xylitol, and yacón syrup. Artificial sweeteners are to be avoided.
Atkins: Three artificial sweeteners are allowed on the Atkins diet: sucralose (Splenda), acesulfame potassium (Sweet One, Swiss Sweet), and saccharin (Sweet ‘N Low). These sweeteners are often mixed with a bulking agent resulting in the addition of carbs. The total of these carbs should be included in one’s daily total.
This is one category where low-carb diets vary greatly.
Paleo: Dairy is completely prohibited on the Paleo diet, although some dieters make an exception for butter.
Keto: Most full-fat dairy products are allowed on the Keto diet; however, one should be cognizant of the carbs within certain products such as cheese. An intolerance to dairy may inhibit weight loss (8). If this is the case, it suggested that all dairy be restricted for several weeks to allow the intestinal track time to heal. After a period of being dairy-free, one might be able to tolerate dairy again in limited quantities.
Atkins: Essentially unlimited portions of butter and cream are allowed on the Atkins diet. Cheese is also acceptable, however, if it contains any carbs, those should be added to daily total.
Meat is generally a staple on low-carb diets. (Vegetarian low-carb plans are outside the scope of this article.)
Paleo: The Paleo diet puts the preference on protein when choosing meat. Meats with more protein and less fat are ideal. Skinless turkey breast which is approximately 92% protein and only 8% fat is desired over fattier meats such as lamb chops which are more than 50% fat. Bacon and all processed meats should be avoided.
Keto: Because the Keto diet focuses on increasing fat and limiting protein, preference is given to fatty meats over lean meats. For instance, it is recommended that one choose 80/20 ground beef over its leaner 93/7 counterpart. Likewise, it is suggested to add butter or a fat-rich sauce to leaner cuts of meat such as beef tenderloin. And, not only is eating bacon allowed, cooking with bacon fat is acceptable.
Atkins: Eating liberal quantities of meat until satiated is acceptable on the Atkins diet. Essentially any meat is allowed.
GRAINS, BREADS, AND PASTAS
For the most part, all grains are prohibited from low-carb diets, especially at the beginning (9). In some cases, very small quantities may be added in during maintenance.
Paleo: The Paleo diet discourages the inclusion of grains, breads, and pastas.
Keto: The Keto diet also discourage the inclusion of grains, breads, and pastas. It is possible, however, to make acceptable grain-free bread-like items from ingredients such as eggs, egg white protein, coconut flour, and butter.
Atkins: Like other low-carb diets, the Atkins diet discourages the consumption of grains, breads and pastas. If, however, a person really feels they must have it, one serving of high-fiber, low-carb bread or pasta (no more than 3 net carbs) per day is allowed but warns this may slow or stall weight loss.
While low-carb diets include lots of nutrient-rich foods, it may be necessary to supplement in certain cases.
Paleo: One of the benefits touted by the Paleo diet is that dieters will not need to spend money on supplements with vitamin D being a possible exception. It is suggested that if one does not get enough sun exposure they should consider supplementing or eating foods with high vitamin D levels such as cod liver oil, catfish, tuna, and salmon.
Keto: Whereas Paleo dieters are encouraged to forgo salt, Keto dieters are encouraged to include sea salt in their diet. As insulin levels fall, the kidneys begin to release more fluids taking it with it essential sodium (10). It is recommended that Keto dieters make sure they are getting enough sodium in the form of sea salt or bone broth. The diuretic effect can also cause the loss of potassium as well. To avoid losing muscle mass, Keto dieters may consider taking a 200-millagram supplement of potassium or be sure to include potassium-rich foods in their diet. Potassium-rich keto-approved foods include: halibut, broccoli, salmon, tuna, avocados, paprika, and other dried herbs such as parsley, basil, and dill. Keto dieters should also monitor their magnesium levels and take a supplement if necessary (11).
Atkins: It is suggested that Atkins dieters take a multivitamin including potassium, magnesium, calcium but without iron.
Encouraging the consumption of water is one aspect all diets seem to agree upon. Water is critical—especially on a low-carb diet. Water keeps the body hydrated, aids in relieving constipation, and assists with the elimination of fat-burning byproducts.
Paleo: Water, coffee, tea, diet soda, and mineral water are allowed on the Paleo diet. Alcoholic beverages are also allowed: two 4-oz glasses of wine, one 12-oz beer, or 4 ounces of a spirit. It is suggested that a glass of wine before or during dinner may help improve insulin sensitivity and reduce appetite.
Keto: The ketogenic diet is probably most notorious for adding butter, coconut oil, or MCT oil to coffee (12). It’s a great way to get some fat into your diet first thing in the morning. Teas, seltzer waters, and stevia-sweetened soft drinks are also allowed. While alcohol is not encouraged, if one chooses to have an occasional drink, they should choose hard alcohols such as whiskey, tequila, rum, vodka, gin, or brandy and avoid any sugary mixers (13).
Atkins: The Atkins diet recommends drinking at least eight 8-oz glasses in addition to other beverages throughout the day. While coffee, tea, and soft drinks are allowed, excess caffeine should be avoided (14). Alcohol while not considered part of the program is allowed on occasion provided the dieter is not diabetic or has trouble controlling how much to drink. Dry wines and low-carb spirits such as vodka and gin are preferred. Beer and liqueurs should be avoided due to their high carb content.
While there are some subtle and some not-so-subtle differences between various low-carb diets, knowing the basics will help you choose which direction you wish to go. There are many more details to each plan. I encourage you to research each plan further before making a decision, and as always, be sure to check with your doctor before making any major changes in your diet. In vary degrees, low-carb diets tend to stabilize blood sugar levels (15) resulting in less cravings (16). Along, with the satiating feeling of eating higher-fat, nutrient-dense foods, dieters typically reduce their caloric intake naturally and ultimately lose weight (17).
(1) Shell, E. R. (2012, June 11). Time to retire the low-carb diet fad. Retrieved September 27, 2018, from https://www.theatlantic.com/health/archive/2012/06/time-to-retire-the-low-carb-diet-fad/258343/.
(2) Wheless, J. W. (2008). History of the ketogenic diet. Epilepsia, 49 Suppl 8, 3–5. https://doi.org/10.1111/j.1528-1167.2008.01821.x.
(3) Kris-Etherton, P. M., & Fleming, J. A. (2015). Emerging nutrition science on fatty acids and cardiovascular disease: nutritionists’ perspectives. Advances in Nutrition (Bethesda, Md.), 6(3), 326S–37S. https://doi.org/10.3945/an.114.006981.
(4) Paleo diet: Eat like a cave man and lose weight? (n.d.). Retrieved September 27, 2018, from http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/paleo-diet/art-20111182.
(5) How does a low carb diet work. (n.d.). Retrieved September 27, 2018, from https://www.atkins.com/how-it-works.
(6) Westman, E. C., Mavropoulos, J., Yancy, W. S., & Volek, J. S. (2003). A review of low-carbohydrate ketogenic diets. Current Atherosclerosis Reports, 5(6), 476–483. https://www.ncbi.nlm.nih.gov/pubmed/14525681.
(7) Masood, W., & Uppaluri, K. R. (2018). Ketogenic diet. In StatPearls. Treasure Island (FL): StatPearls Publishing. Retrieved from http://www.ncbi.nlm.nih.gov/books/NBK499830/.
(8) Can hidden food or dairy allergies cause weight gain? (2013, April 15). Retrieved September 28, 2018, from https://www.denverpost.com/2013/04/14/can-hidden-food-or-dairy-allergies-cause-weight-gain/.
(9) Sánchez-Chino, X., Jiménez-Martínez, C., Dávila-Ortiz, G., Álvarez-González, I., & Madrigal-Bujaidar, E. (2015). Nutrient and nonnutrient components of legumes, and its chemopreventive activity: a review. Nutrition and Cancer, 67(3), 401–410. https://doi.org/10.1080/01635581.2015.1004729.
(10) Tiwari, S., Riazi, S., & Ecelbarger, C. A. (2007). Insulin’s impact on renal sodium transport and blood pressure in health, obesity, and diabetes. American Journal of Physiology. Renal Physiology, 293(4), F974-984. https://doi.org/10.1152/ajprenal.00149.2007.
(11) Maggio, M., De Vita, F., Lauretani, F., Nouvenne, A., Meschi, T., Ticinesi, A., … Ceda, G. P. (2014). The interplay between magnesium and testosterone in modulating physical function in men. International Journal of Endocrinology, 2014, 1–9. https://doi.org/10.1155/2014/525249.
(12) 8 reasons why saturated fats are not that bad. (2013, February 25). Retrieved September 28, 2018, from https://www.healthline.com/nutrition/top-8-reasons-not-to-fear-saturated-fats.
(13) A ketogenic diet and alcohol: can they mix? (2013, October 28). Retrieved September 28, 2018, from https://www.ruled.me/ketogenic-diet-and-alcohol/.
(14) LD, J. C., RDN. (n.d.). The effects of coffee on a low carb diet. Retrieved September 28, 2018, from https://www.livestrong.com/article/276204-the-effects-of-coffee-on-a-low-carb-diet/.
(15) Branis, N. M., Etesami, M., Walker, R. W., Berk, E. S., & Albu, J. B. (2015). Effect of a 1-week, eucaloric, moderately high-fat diet on peripheral insulin sensitivity in healthy premenopausal women. BMJ Open Diabetes Research and Care, 3(1), e000100. https://doi.org/10.1136/bmjdrc-2015-000100.
(16) Stubbs, B. J., Cox, P. J., Evans, R. D., Cyranka, M., Clarke, K., & de Wet, H. (2018). A ketone ester drink lowers human ghrelin and appetite. Obesity (Silver Spring, Md.), 26(2), 269–273. https://doi.org/10.1002/oby.22051.
(17) Brehm, B. J., Seeley, R. J., Daniels, S. R., & D’Alessio, D. A. (2003). A randomized trial comparing a very low carbohydrate diet and a calorie-restricted low fat diet on body weight and cardiovascular risk factors in healthy women. The Journal of Clinical Endocrinology and Metabolism, 88(4), 1617–1623. https://doi.org/10.1210/jc.2002-021480.