Every couple of years a new low-carbohydrate (low-carb) fad diet pops up and rears its ugly head. First it was the Atkins diet. Then the South Beach and Zone diets sprouted up. Today, we have the paleo and whole 30 diet. But there’s a new kid on the low-carb block—the keto or ketogenic diet.
The keto diet is a high-fat, high-ish protein, and extremely low-carb diet. Along with other low-carb diets, meat, eggs, seafood, oils, and high-fat dairy products like cheese and butter provide the majority of calories. Nuts and low-carb vegetables are also included, but higher-carb vegetables, fruit, potatoes, grains, and beans are excluded, or severely limited. This type of diet is meant to induce a metabolic state called “ketosis”, in which the body is depleted of glucose (carbohydrate) and glycogen (the storage form of glucose). In the absence of glucose, the body produces ketone bodies, which it uses for fuel.
This diet is occasionally used to treat epilepsy in children who aren’t responding to therapy, but it’s often considered a last resort. However, the recent spike in interest over the keto diet isn’t from epileptic children, but from people looking to lose weight and improve their overall health. A quick Google search directs you to numerous websites touting a long list of benefits that you’ll experience if you adopt a keto diet. These claims, which are often mentioned without any supporting study or link, include: weight loss, improved diabetic control, improved mental focus, increased energy, improved cholesterol levels, better skin, improved gastrointestinal health, reduced sugar cravings, improved blood pressure, migraine control, improved heartburn, reduced ADHD symptoms, and it is even mentioned as a treatment for polycystic ovarian syndrome and brain cancer.
Sound too good to be true? That’s because it is. All of these claims are either blatantly false, misleading, or true but come at the expense of our overall health. And most of us would never know this if we just scanned the top layer of these websites. But when we get our hands deep into the data, it becomes quite clear that a keto diet is not ideal for human health and is hazardous to our long-term health.
When I reviewed the data, I only found a few (non-epilepsy) studies looking specifically at a keto diet. There are, however, a fair amount of studies looking at low-carb diets, which is essentially what the keto diet is. In fact, many of the pro-keto websites I reviewed use low-carb diet studies to support their claims. The problem with many of these studies is that they were funded by the Atkins Diet Foundation, or some other organization that is financially benefiting from low-carb diets/products/books/etc. These studies are designed to produce favorable results, which are then used to market and sell their fad diet and products. There is an obvious conflict of interest at play.
So, just like we wouldn’t use tobacco industry studies to decide if cigarettes are healthy, or egg industry studies to determine if eggs are healthy, we’re not going to use these biased studies when looking at the health implications of a low-carb diet (although I did still review these). When we exclude biased studies, we’re still left with a good amount of data. Based on that data, here are my top four reasons we should avoid a keto diet.
1. It Is The Opposite Of What We Should Be Eating For Ideal Health
Because of its high-fat, higher-protein, and low-carb nature, a keto diet is typically centered on animal products. Meat, high-fat dairy, eggs, seafood, and oil tend to provide the majority of calories, while higher-carb vegetables, fruit, beans, and grains are excluded or severely limited.
This type of diet is the complete opposite of what the overall evidence on diet and nutrition suggests we should be eating. The data is quite clear that humans should consume a diet of primarily, or entirely, unprocessed, plant-based foods. We should center our diet on the exact foods that are avoided while on a keto diet. Whole grains, beans, fruits and vegetables should provide the majority of our calories, whereas high-fat animal products should be limited or avoided.
This message is echoed by all major health organizations, from The American Cancer Society to the World Health Organization. Eating a predominantly plant-based diet was also the main focus of the 2015 Scientific Advisory Committee’s recommendations for the USDA food guidelines (before the food industry flexed its muscle).
It comes with no surprise that all of the healthiest, longest-living populations in the world consume a diet that is nearly the exact opposite of a keto diet. People living in “Blue Zones” (a term coined by National Geographic’s Dan Buettner to describe places in the world where people tend to live the healthiest and longest lives) all eat a diet rich in unprocessed, high-carbohydrate foods, such as beans, whole grains, potatoes, fruits, and vegetables. In fact, high-carb sweet potatoes provide two-thirds of the calories in the traditional diet of Okinawa, Japan—a place that boasts the longest life expectancy for women.
Regardless of how many pro-keto websites tell us that “we got it all wrong” when it comes to nutrition, we didn’t, and we still don’t. The overall message that we should eat a diet centered on unprocessed plants while limiting animal products and processed foods has been the mainstay of nutrition recommendations for decades. Diets rich in unprocessed plant-based foods are consistently and overwhelmingly associated with better health and a longer life, while diets centered on animal products and devoid of fruit, whole grains, and beans, are consistently and overwhelmingly associated with chronic diseases and premature death.
Many of the foods avoided on a keto diet are the exact foods we should be eating for ideal health and longevity. Beans are the food most associated with healthy ageing, while whole grains are consistently associated with lower rates of death and chronic disease (1-2). A lack of fruit in our diet is one of the most prominent dietary risk factors contributing to our global disease burden (3). These foods shouldn’t be avoided, but encouraged. Anyone who says otherwise is not referencing evidence-based information and has a severe lack of insight on the overall data as it pertains to human health and nutrition.
2. You’ll Lose Weight…But It Won’t Last
People tend to initially lose weight on a low-carb diet, whether it be a keto diet, Atkins diet, or whole 30 diet. In fact, people tend to lose weight very rapidly on a low-carb diet. But there’s a catch.
A majority of the initial weight loss is a reflection of water loss, not fat loss. When we stop eating glucose (carbohydrate) we eventually deplete our body of its glucose stores (called glycogen). Glycogen is bound to water, so when we burn through stored glycogen, we shed and excrete the water it was bound to. This makes a big difference on the scale, as one liter of water weighs 2.2 pounds. I’ve weighed myself before and after playing a couple hours of outdoor basketball on a hot day and I can easily drop five pounds in two hours by simply sweating off water. Knowing that it’s water weight, I’ll obviously rehydrate and gain that weight back, but people on low-carb diets see that initial, rapid weight loss and mistake it for fat loss.
After the initial loss in water weight, the weight loss that follows is typically the result of a reduced calorie intake. Although there are some exceptions, weight balance is determined by calorie balance. In other words, if you consume more calories than you burn, you’ll gain weight. And if you consume fewer calories than you burn, you’ll lose weight. People on a keto diet tend to reduce the number of calories they consume for a variety of reasons: The high-fat meals have a satiating effect, sugary foods and beverages are avoided (think candy bars and soda), feelings of nausea, loss of appetite, or malaise set it, or because the diet itself is extremely restrictive. Each of these, and/or the combination, work to lower total calorie intake, which will result in weight loss.
Anytime calories are reduced below your metabolic needs, you’ll lose weight. This holds true regardless of what you’re actually eating. To prove this point, a nutrition professor at Kansas State University went on a “Twinkie diet” that consisted of Little Debbie snacks, Doritos, Oreos, and other junk food. He kept his caloric intake, however, around 1,800 calories per day—about 1,000 calories less than he metabolically needed to maintain weight. And sure enough, after two months he had lost 27 pounds. All weight loss diets work in a similar fashion—they get people to eat fewer calories. The most important question, however, is whether a low-carb diet is more effective than other weight loss diets?
Many studies compare low-carb diets to low-fat or other calorie-restricted diets and find that low-carb diets result in more initial weight loss. The problem is, these studies tend to last only a few weeks or months. Given what we know about the rapid water loss on low-carb diets, this isn’t a surprise (those who financially benefit from low-carb diets know this and design studies to exploit it). In fact, most low-carb weight loss studies rarely reach one year in duration. The studies that do last more than a year, overwhelmingly show that low-carb diets do not result in any more long-term weight loss, compared to other weight loss diets (even studies funded by the Atkins Foundation fail to show any advantage of their diet over the long term) (4-11). I should point out, however, that most “diets” don’t lead to long-term weight loss. And the keto diet is no exception.
People who go on low-carb diets rarely stick to them. And many find themselves going on and off these diets with their weight yo-yoing as a result. This cycle of weight gain and weight loss is not good for our health. It slows down our metabolism and makes future weight loss that much harder. If you are looking to break the vicious cycle of on/off dieting, I would encourage you to read the book “The End of Dieting” by Dr. Joel Fuhrman, M.D.
Low-carb diets, including the keto diet, lead to a rapid loss in water weight. Any further weight loss is the result of calorie restriction, not some low-carb magic. Do not be fooled by studies that boast greater weight loss with low-carb diets, as these are typically conducted over a short duration. Long-term studies show that low-carb diets are no better than any other calorie-restricted weight loss diet (although most “diets” are not effective over the long term). Just like the “Twinkie diet”, a low-carb diet can lead to weight loss if calories are kept in check, but neither are preferred for long-term, overall health.
3. There Are Many Potential Negative Side Effects
A healthy diet should improve our health and make us feel better. This doesn’t appear to be the case with a keto diet. Websites profiting off a keto diet are more than willing to share individual testimonies about how the diet helped someone lose weight and feel great. It’s hard to dispute these anecdotal reports. But I’ve also reviewed every study on a keto or low-carb diet that I could get my hands on and found that many people who are placed on such a diet experience a variety of negative side effects. In some studies, unwanted side effects were reported in over 50% of participants following a keto diet (12). Even pro-keto websites acknowledge the following side effects, which include:
- Back pain
- Kidney stones
- Increased calcium loss
- Heart palpations
- Flu-like symptoms
- Foul-smelling breath
Another unwanted side effect reported in some studies, is an increase in LDL (bad) cholesterol levels. Typically, when someone loses weight, regardless of how (drug addiction, cancer, starvation), their cholesterol levels tend to improve. This happened in the Kansas State professor who went on the “Twinkie diet”. Because he lost weight, despite his junk food diet, his LDL cholesterol dropped by 20%, HDL (good) cholesterol increased by 20%, and his triglycerides decreased by 39%. This same effect occurred in a few of the weight loss studies, but others showed that a low-carb diet negates the cholesterol-improving effect seen with weight loss, especially when compared to a low-fat diet (12-17). In some instances, participants on a low-carb diet needed to increase their cholesterol medication or start taking a cholesterol-lower drug (13; 15). The goal of a healthy diet should be to reduce the amount of medication needed, not increase it.
On top of this, low-carb diets have been shown to impair blood flow, which is not what any of us want, but especially people with a history of, or at risk for, cardiovascular disease (18-20). With the ability to negate weight loss-induced improvements in cholesterol, while impairing blood flow, it’s no surprise that low-carb diets have been linked to an increased risk of cardiovascular disease (21).
Another potential long-term side effect is an increased risk of cancer. Not only does a keto diet limit or avoid foods that are known to help protect against cancer, such as fruit, whole grains, and beans, but the diet’s high amount of animal protein may increase our cancer risk by increasing something called insulin-like growth factor 1 (IGF-1). IGF-1 appears to play a role in the development of cancer, metastasis of cancer, and may even protect cancer cells from anti-cancer treatments (18). Having higher levels of IGF-1 is associated with an increased risk of numerous cancers, including breast and prostate (19-23). Studies show that diets rich in animal protein boosts IGF-1 levels, while consuming your protein from plants is associated with significantly lower levels (24-30). The increase in IGF-1 caused by animal protein is likely one of the many reasons the American Cancer Society encourages people to eat a diet that emphasizes plants, such as whole grains, fruit, vegetables, and beans, while avoiding red and processed meat. Again, the opposite of a keto diet.
4. A Keto Diet May Shorten Your Lifespan
Remember those healthy, long-living “Blue Zone” populations thriving on a diet rich in whole grains, fruit, vegetables, and beans—a diet that is almost the complete opposite of a keto diet? It should come as no surprise then that following a low-carb, keto-like diet is consistently associated with increased mortality (31-35). In other words, long-term adherence to a low-carb diet appears to increase one’s risk of premature death. Many of these studies also show that low-carb diets based on animal products are positively associated with death and disease, while diets based on plants, whether lower in carbs or not, are negatively associated with death and disease (31; 35-38).
This is my main concern with animal-based, low-carb diets. They sacrifice our long-term health for perceived short-term improvements that tend to not last. As Dr. Michael Greger, M.D. has bluntly pointed out: low-carb diets are great…if you want a skinnier casket.
The keto diet has become the fad diet du jour. Its mechanisms of action and supportive arguments are nothing new, as they are simply a regurgitation of the original low-carb Atkins diet. Do not be fooled by the “quick-fix” nature of this diet. Its superficial short-term benefits rarely last and come at the expense of our overall and long-term health. Instead, stick to a diet that is supported by the overall evidence and consumed by the healthiest, longest-living populations on earth—a diet rich in unprocessed, plant-based foods, such as whole grains, beans, fruit, vegetables, nuts and seeds.
Peace, Love, Health
- Legumes: the most important dietary predictor of survival in older people of different ethnicities.
- Whole grain consumption and risk of cardiovascular disease, cancer, and all cause and cause specific mortality: systematic review and dose-response meta-analysis of prospective studies.
- A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010.
- A Randomized Trial of a Low-Carbohydrate Diet for Obesity
- Effects of low-carbohydrate vs low-fat diets on weight loss and cardiovascular risk factors: a meta-analysis of randomized controlled trials.
- What are the long-term benefits of weight reducing diets in adults? A systematic review of randomized controlled trials
- Weight and Metabolic Outcomes After 2 Years on a Low-Carbohydrate Versus Low-Fat Diet: A Randomized Trial
- Long-Term Effects of 4 Popular Diets on Weight Loss and Cardiovascular Risk Factors A Systematic Review of Randomized Controlled Trials
- Four-Year Follow-up after Two-Year Dietary Interventions
- Three-Year Weight Change in Successful Weight Losers Who Lost Weight on a Low-Carbohydrate Diet
- The effects of a low-carbohydrate versus low-fat diet on adipocytokines in severely obese adults: three-year follow-up of a randomized trial
- The effect of a low-carbohydrate, ketogenic diet versus a low-glycemic index diet on glycemic control in type 2 diabetes mellitus
- A low-carbohydrate, ketogenic diet to treat type 2 diabetes
- 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
- A Low-Carbohydrate as Compared with a Low-Fat Diet in Severe Obesity
- Comparison of isocaloric very low carbohydrate/high saturated fat and high carbohydrate/low saturated fat diets on body composition and cardiovascular risk
- A Randomized Trial of a Low-Carbohydrate Diet for Obesity
- Negative effect of a low-carbohydrate, high-protein, high-fat diet on small peripheral artery reactivity in patients with increased cardiovascular risk.
- The effect of high-protein diets on coronary blood flow.
- Low-carbohydrate diets impair flow-mediated dilatation: Evidence from a systematic review and meta-analysis
- Low carbohydrate-high protein diet and incidence of cardiovascular diseases in Swedish women: prospective cohort study
- The type 1 insulin-like growth factor receptor pathway.
- Insulin-like growth factor (IGF)-I, IGF binding protein-3, and cancer risk: systematic review and meta-regression analysis.
- A prospective study of plasma insulin-like growth factor-1 and binding protein-3 and risk of colorectal neoplasia in women.
- Prospective study of colorectal cancer risk in men and plasma levels of insulin-like growth factor (IGF)-I and IGF-binding protein-3.
- Insulin-like growth factor 1 (IGF1), IGF binding protein 3 (IGFBP3), and breast cancer risk: pooled individual data analysis of 17 prospective studies
- Circulating insulin-like growth factor peptides and prostate cancer risk: a systematic review and meta-analysis.
- The Associations of Diet with Serum Insulin-like Growth Factor I and Its Main Binding Proteins in 292 Women Meat-Eaters, Vegetarians, and Vegans
- Hormones and diet: low insulin-like growth factor-I but normal bioavailable androgens in vegan men
- A low-fat, whole-food vegan diet, as well as other strategies that down-regulate IGF-I activity, may slow the human aging process.
- Long-term effects of calorie or protein restriction on serum IGF-1 and IGFBP-3 concentration in humans
- Animal protein intake, serum insulin-like growth factor I, and growth in healthy 2.5-y-old Danish children.
- Dietary Correlates of Plasma Insulin-like Growth Factor I and Insulin-like Growth Factor Binding Protein 3 Concentrations
- Low Protein Intake Is Associated with a Major Reduction in IGF-1, Cancer, and Overall Mortality in the 65 and Younger but Not Older Population
- Low-carbohydrate diets and all-cause and cause-specific mortality: Two cohort Studies
- Low-Carbohydrate Diets and All-Cause Mortality: A Systematic Review and Meta-Analysis of Observational Studies
- Low carbohydrate-high protein diet and mortality in a cohort of Swedish women.
- Low-carbohydrate-high-protein diet and long-term survival in a general population cohort.
- Mediterranean and carbohydrate-restricted diets and mortality among elderly men: a cohort study in Sweden
- Low-carbohydrate diet scores and risk of type 2 diabetes in men.
- Dietary protein and risk of ischemic heart disease in middle-aged men
- Low-carbohydrate-diet score and the risk of coronary heart disease in women.