Eat Fat to Burn Fat? The Skinny on the Ketogenic Diet

This is the second in a series of collaboration between Don’t Eat the Pseudoscience and In Defense of Processed Food. Head over to the site and explore, and stay tuned for more! Check out our first collaboration HERE!

Last week I went to a birthday party. Andrew, the birthday boy, shared that he’d been on the ketogenic diet for 3 months. He’d lost 10 pounds and felt great. The party food was fatty and delicious–we dined on jalapeno poppers with cheddar cheese and bacon, made our own beef and pork tacos with shredded cheese, bell peppers, and onion in lettuce wraps, and at the end celebrated with a low-sugar peanut butter cake covered in whipped cream and dark chocolate. Chips and tortillas were available for the non-keto eaters, and a wonderful time was had by all.

The ketogenic or “keto” diet has skyrocketed in popularity over the past few years, reaching the highest interest in the summer of 2018. It is heavy in proteins and fats, encouraging users to consume meats, eggs, cheeses, fish, nuts, butter, oils, seeds, and fibrous vegetables. The goal of the keto diet is to bring carbohydrates down to less than 5% of a person’s daily calories by eliminating most grains, fruit, starchy vegetables, legumes, and sweets and replacing those calories with fat.

This isn’t the first time we’ve heard the hype about low-carb diets. The Atkins diet, which became popular back in the 70’s, recommended consuming fewer carbohydrates and replacing those calories with high protein and fat. The ketogenic diet takes it one step further by advocating for even further carbohydrate reduction and increased fat, which shifts the body’s metabolism into burning fat.

Carbohydrates are the easiest to metabolize and thus the body’s first choice for energy. During metabolism, carbs are broken down into glucose molecules which are either immediately used to fuel our tissues or converted into glycogen, a storage form of glucose in the liver and muscles. Excess glucose is stored in the body as fat. In contrast, fats are broken down into smaller molecules known as ketones and fatty acids, which are then transformed into components which can be used as energy.

While the Dietary Guidelines for Americans recommends that carbohydrates make up 45 to 65 percent of total daily calories, the ketogenic diet recommends consuming 5-10% carbohydrates, 20-25% protein, and 70-80% fat. “Going keto” or beginning a ketogenic diet means the body must switch to metabolism of fats as a supply of energy to accommodate the lack of carbs. This typically happens when one consumes only 20-50g of carbohydrates per day for two to four days. The body is flooded with ketones as it moves to a lipid metabolism, inducing a metabolic condition called ketosis or ketogenesis, which gives the diet its name.

The body experiences several changes as it shifts to accommodate the new form of calories. First, the glycogen stores in the body disappear. Glycogen is bound up in water, so dieters will find themselves needing to urinate frequently as their bodies deplete these stores. The loss of glycogen and glycogen-bound water results in immediate weight loss, which may be encouraging to dieters. In addition, the process of transitioning from a glucose metabolism to a lipid metabolism may cause symptoms that some have termed the “keto flu.”  The most common symptoms include headache, fatigue, nausea, dizziness, irritability, leg cramps, constipation, bad breath, and heart palpitations. Ketogenic diet patients reported fatigue, headache and diarrhea during their first week, peaking on day 4 and leveling off after day 7. These symptoms may be due to sugar withdrawals and electrolyte deficiency from water loss.

The ketogenic diet was originally developed in 1921 as a therapeutic diet for epileptic patients. Fasting was known to be effective in reducing seizures and doctors discovered that a very high fat, low carb diet could simulate the metabolic effects of fasting or starvation by forcing the body to use primarily fat as a fuel source. During fasting, the fatty acid breakdown from the body metabolizing fat stores produces certain ketone bodies which are able to cross the blood-brain barrier and provide anticonvulsant properties in the brain. While the exact mechanism by which this happens is unclear, some theories indicate that this change in fuel production could make brain cells more resilient in the face of metabolic demands during seizures or the presence of ketone bodies may favor the synthesis of a “calming” inhibitory neurotransmitter called GABA. Treating epilepsy with the ketogenic diet instead of anticonvulsants can relieve patients from medication with known negative cognitive and behavior effects.

Blocking glucose metabolism has been highly effective in reducing seizures in epileptic patients, and has also shown promise for promoting healthy blood sugar in type 2 diabetics in the short-term , although a review found no difference found after the first year of treatment. It can be challenging to discern dietary impact—one meta-analysis found there to be no difference in glycemic control between those on a low carb diet and those on a high carb diet. They suggested that the lack of effect may be because patients were unable to achieve the strict prescribed carbohydrate intake of as little as 20g.  The benefits from the ketogenic diet only come about when people go into ketosis and eating more than 20g a day prevents ketosis. The keto diet is also currently being investigated as a medical intervention for polycystic ovary syndrome, neurodegenerative diseases, and cancer as blocked glucose metabolism has been correlated with reduced brain and body inflammation in mice.

The current keto-hype, however, is about weight loss. The ketogenic diet claims to aid in weight loss in two ways. First, by forcing the body to burn fat, which takes more energy to digest and break down than carbohydrates. This is referred to as “increased energy expenditure”. Second, by reducing the consumption of calories through a feeling of fullness or reduced appetite due to the floating ketone bodies in the blood.

There are many promising studies that show weight loss from a ketogenic diet for up to one year.  One put participants on a strict ketogenic diet, even measuring ketones in blood/urine to validate ketogenesis. Over a 6 week period they observed mild weight loss.  Another with 132 severely obese patients found that participants on a carbohydrate-restricted diet lost more weight than those than on a calorie- and fat-restricted diet.

A third study had participants alternate between a ketogenic diet, a low-carb non-ketogenic diet, and a normal Mediterranean diet. Significant weight loss and reduction of body fat percentages were observed only during ketogenic periods compared to the two other diets. In addition, if the patients complied with the prescribed Mediterranean diet (which was relatively strict: 1800 kcal/day) during the maintenance period, no weight regain was observed at 12 months.

A big challenge in studying the ketogenic diet is poor adherence. To ensure compliance, one study confirmed 17 overweight volunteers to metabolic wards for 8 weeks. The first four weeks they ate a high-carbohydrate, high sugar diet and the second four they were switched to a carefully designed low-carbohydrate low-sugar diet. After switching to the keto diet participants immediately lost an average 3.5 pounds, which was attributed to body water loss. Over the 28 day ketogenic diet period the participants lost 4.8 pounds with 1 pound from body fat while consuming about 300 fewer calories per day. Overall, the ketogenic diet increased energy expenditure by ~100 calories/day after adjusting for body weight and composition, which was complicated by the loss of weight from water. Researchers concluded that the ketogenic diet contributed to weight loss and increases in energy expenditure that were near the limits of detection.

The initial data we have about the ketogenic diet shows positive results in weight loss, but we have less data on long-term effects of this diet with regard to losing weight and keeping it off, as well as the enduring effects on health.  In mice we have seen that a high-fat diet may cause initial weight loss and then over time rebound in weight but this has not been shown in humans. A review article published in the journal Diabetes suggests that we need additional data to draw definite conclusions about this diet, which would come from robustly controlled long-term studies (minimum of 2 years) in which carbohydrate, fat, energy and dietary fiber intake are carefully monitored along with changes in body weight.

While the ketogenic diet has been shown to help with weight loss, the drastic metabolic shift comes with potential negative physiological effects. One of the biggest concerns doctors cite about the ketogenic diet is the impact on liver and kidneys, as well as the small possibility of ketoacidosis which is when the blood becomes acidic due to a ketone build-up. Keto dieters are at an increased risk for developing kidney problems, potentially including kidney failure. Patients on the keto diet are typically urged to supplement with oral potassium citrate to reduce or delay the production of painful kidney stones,which occurred in 6.7% of one study’s participants. In addition, rodents put on the ketogenic diet have shown development of non-alcoholic fatty liver disease and insulin resistance, although we have not yet seen the same results in humans.

Another side-effect of the ketogenic diet is that physical activities may be more exhausting. Patients following the ketogenic diet experienced a negative impact on physical performance, including reduced endurance capacity, maximum work load and faster exhaustion. The reduction in peak power is likely due to lowered muscle glycogen stores from decreased carbohydrates. The study found that physical fitness was not impacted in a way that would impair daily life, but may be a matter of concern for competitive athletes.

One review of studies found that participants on low carb diets lost more weight compared to participants on low fat diets, but also increased their LDL cholesterol.  Increased LDL-cholesterol, or “bad cholesterol” is associated with a higher risk of cardiovascular disease. A separate meta-review concluded that low-carbohydrate, non-energy-restricted diets appear to be at least as effective as low-fat, energy-restricted diets in inducing weight loss for up to 1 year.  However, just like the previous review they noted unfavorable changes in LDL-cholesterol.

Some of the physiological repercussions of this diet may depend on what types of foods are being consumed instead of carbohydrates. A study tracking the long-term effects of dietary carbohydrates on mortality found that both high and low percentages of carbohydrate diets were associated with increased mortality, with the lowest risk observed at 50–55% carbohydrate intake. They observed that low-carb diets that replace carbohydrates with proteins and fat from animal sources were associated with higher risk of mortalitycompared to those that replace carbohydrates with proteins and fats from plant sources.

In a review of all current diets including Paleo, Vegan, Gluten-free, Whole30, and more, US News Health ranked the Keto diet 39th—dead last. Concerns include repercussions for cycling in and out of the diet, and that it can be especially risky for those with liver or kidney concerns, who should avoid it altogether. One major downside of the Keto diet is that it doesn’t specify the type of fats to replace carbs, despite decades of prior research indicating that animal-based proteins and saturated fats are linked to increased risk of cardiovascular disease. Another concern is that a diet containing 70% fat may be naturally lower in fruits and vegetables, which could lead to deficiency in vitamins and minerals and a decline in overall health.

In addition to the physiological concerns, there are also more practical ones. The Keto diet may be a challenge to maintain over time and may not work with everyone’s lifestyle.  To be a true Keto diet adherent, a diet must be <10% carbohydrates and >60% fat to induce and maintain the increased levels of circulating ketone bodies. To stay in a state of ketosis one must constantly maintain a certain percentage of carbohydrates, meaning that a slice of cake at a company party is enough to throw the metabolism back to burning carbs and storing fat.

A recent review paper summarizes the current state of affairs: “results regarding the impact of such diets on cardiovascular risk factors are controversial, both in animals and humans, but some improvements notably in obesity and type 2 diabetes have been described. Unfortunately, these effects seem to be limited in time, and more studies are therefore warranted to better assess the effects of a long-term ketogenic diet.”

So what should we say to the Andrews of the world, or to those who are considering making the leap? Ultimately there isn’t enough data for us to fully understand the long-term effects and it’s not clear at what point the benefits outweigh the risk, particularly to vulnerable populations or those with other health issues. While many dieters have seen drastic weight loss after the ketogenic diet, and there are many enthusiasts withand without medical credentials, the choice to make a big metabolic change should only be done after consulting with a doctor.

If you have chosen to make the leap, let us know about your experiences in the comments! Please invite me to all your fun keto parties and in the mean time I’ll be sure to eat enough donuts for both of us.



Erica Kenney is a food scientist with a BS from UC Davis and a MS from University of Georgia. Her master’s thesis was on the emotions of coffee drinking and she’s particularly interested in how people feel about their food. Doesn’t everybody have a lot of feelings about their food? She worked in product development with fruits and vegetables, as a technician in a flavor lab, and currently works as a sensory analyst at E&J Gallo Winery.

The Magic Behind the Unicorn Frappuccino

If you haven’t heard of the latest come-and-gone Starbuck’s craze, you must be living under a rock! The Unicorn Frappuccino, AKA the most Instagrammable drink on the market, has swept across the nation. This bane of baristas has already been criticized for being a veritable sugar bomb. Now, when people are buying frappuccinos they aren’t doing it for their health. In general, frappuccinos in are a treat to be enjoyed every now and then. Let’s be honest here, the Unicorn frapp isn’t even the most sugary thing on the Starbuck’s menu board. That  aside, let’s talk about what makes the unicorn frapp so cool: dat color doe.

A quick glance at the ingredient list in this magical elixir provides us a glimpse into the beautiful cacophony. The magical ingredients we’re most interested in here are the Sour Blue Powder and the Pink Powder. The blue hue is provided by spirulina, a blue-green algae, and the pink comes from a mix of fruits and vegetables, including apple, cherry, radish, and sweet potato. The real magic happens happens when you mix your frappuccino and watch it turn from purple to pink!

But is it magic? Or, more likely…chemisty? The other secret here is the citric acid in the sour blue powder. As you mix the drink, the citric acid is mixed in causing the whole drink to become more acidic, which is also why the flavor changes from sweet to sour.

But why does this cause the color to change?

The pigments responsible for the color in the pink powder are anthocyanins. Anthocyanins are present in many fruits and vegetables including blueberries, cranberries, red cabbage, and eggplant. These molecules have a special property that causes them to change color based on the pH. When the citric acid dissolves, the pH shift causes the drink to become more acidic (lower pH); this causes the anthocyanins, which start out purple, to change their structure slightly, and thus appear beautifully pink!

So, if you’re sipping this exciting new concoction while you scroll through the comments from all your jealous Instagram followers, remember… you have chemistry to thank! It’s not magic, it’s science (so don’t eat the pseudoscience)!


John in unicorn mode

Hailing from central California, John is a PhD candidate (Update: he did it! Dr. Frelka to you!) at Ohio State University studying how processing affects the physical properties of different food products. John has a B.S. and M.S. in Food Science from UC Davis where he studied both consumer food science and food microbiology. As a self-proclaimed nerd, John spends his free time reading comic books and playing board games. According to John, the major food groups are coffee, beer, and buffalo chicken dip. (Follow him on Twitter! @madfoodscience)


MSG: Friend or Foe?

“The most prominent symptoms are numbness at the back of the neck, gradually radiating to both arms and the back, general weakness and palpitation.”

This terrifying set of symptoms sounds like a heart attack, but is actually the description of the ailments of “Chinese Restaurant Syndrome” as described by Dr. Robert Ho Man Kwok in a letter to the editor for the New England Journal of Medicine. Dr. Kwok claimed that he would consistently experience this syndrome after consuming Northern Chinese fare with his colleagues. In the letter, he attributed these symptoms to one of three possible culprits: cooking wine, excess levels of salt, or monosodium glutamate (MSG) used in the food. A number of individuals soon followed with similar letters affirming that they too had experienced this set of symptoms. As MSG is the only ingredient that differentiates Chinese food from other restaurant cuisines, MSG became the sole antagonist for this so-called Chinese Restaurant Syndrome. And thus MSG became enemy #1 overnight after a single a non-expert letter to the editor.

MSG is used as an ingredient to elicit the savory flavor, or umami taste, in foods. As the newest addition to the basic tastes, umami is less recognizable than sweet or salty. Our perception of umami is generally attributed to our evolutionary roots. Amino acids, the building blocks of proteins, elicit the flavor of umami which could have signaled to our early ancestors that a specific food was a good source of protein. Glutamic acid is a specific amino acid that triggers umami taste. Adding a sodium molecule to glutamic acid yields the compound we know as monosodium glutamate, or MSG.

Much of the research around umami and MSG is from Japan. Soups are often prepared with seaweed in Japanese cuisine to deliver a unique savory flavor. In the early 20th century, salts of glutamic acid like MSG were isolated in natural soup preparations that use seaweed as an ingredient, revealing that MSG was a primary source of that desirable flavor. While the idea to add pure MSG as an ingredient to foods in order to increase the perception of savory came much later, the practice of adding MSG-containing ingredients has been around for a long time. For example, breaking down or hydrolyzing proteins using heat or aging processes like fermentation creates these free amino acids which elicit umami taste. That’s why hydrolyzed vegetable protein or hydrolyzed yeast extract (hello, Marmite and Vegemite!) are such popular ingredients around the world. Ask any chef, and they’ll tell you that the ideal dish is one that balances the five basic tastes creating a deeper and more lasting flavor profile.

From Ink Chromatography Blog

MSG has been a gras (generally recognized as safe) food ingredient since 1958 by the FDA, and the Codex Alimentarius categorizes glutamate and all of its various salts as flavor enhancers. However, after the Chinese Restaurant Syndrome came on the scene, MSG became hotly contested as an additive that causes adverse effects like migraines and asthma. In response to this public outcry, a comprehensive safety review was conducted on MSG and other umami-inducing salts in 1987 by the Joint FAO/WHO Expert Committee on Food Additives. They concluded that MSG does not pose a health risk. In fact, they did not deem it necessary to specify a daily intake level as the quantity of glutamate to cause acute toxicity was so high. This was later confirmed in another evaluation in 1991 by the Scientific Committee for Food of the Commission of the European Communities.

On average, Americans consume approximately 0.55 g/day of added glutamate in foods which is similar to the daily consumption in the UK. Compare that to the average Asian consumer who ingests 1.2-1.7 g/day of added glutamate. Additionally, it has been shown time and time again that the human body metabolizes all forms of glutamate the same way—added or naturally-occurring. In fact, contrary to popular thought, glutamate levels in the blood do not increase after foods with high levels of added glutamate are ingested.

In general, there is weak evidence, at best, that links MSG to Chinese Restaurant Syndrome symptoms. In the most comprehensive study to date, a collaborative research project between Boston University, Harvard University, Northwestern University, and the University of California at Los Angeles investigated the effects of glutamate on self-reported MSG-sensitive subjects. Out of the 130 subjects included in the testing, only two had consistent responses to glutamate samples in a double-blind, placebo-controlled, randomized trial. Furthermore, the symptoms themselves were not reproducible among the glutamate-containing samples. This was not a statistically significant response, and keep in mind that these are self-reported sufferers of Chinese Restaurant Syndrome effects. The researchers concluded that glutamate does not cause reproducible sensitivities reported by some consumers.

From Business Insider

In addition to general sensitivity, there have been several specific symptoms “linked” with MSG including hives/swelling, asthma, stuffy nose, and headaches/migranes. The research addressing each of these is outlined below:

Hives/ Swelling (urticaria/ angio-oedema) – Many studies that investigate the link between MSG and these allergic skin reactions are difficult to interpret because subjects are used that are prone to allergic reactions, and they are often asked to refrain from taking any antihistamines during the testing period. This confounds the results because it makes it almost impossible to ascertain what is causing rash-like symptoms. In a study that asked subjects to reduce the antihistamine use to the lowest levels possible, there was no reproducible link between skin swelling and MSG consumption during double-blinded trial. There have been single cases (two) where urticaria and angio-oedema can be caused by MSG ingestion, though this is extremely rare.

Asthma – Similar to the hives studies, asthma studies are convoluted because subjects are used that report asthmatic symptoms to Chinese foods, and those subjects are asked to refrain from asthma medication. It is difficult to separate effects from the consumption of glutamate or withdrawal from preventative attack medication. Furthermore, the results within studies and between studies have not been reproduced in subjects, and it has been reported that no long-term health effects exist in epidemiological studies. There is no consistent evidence that glutamate ingredients trigger asthma symptoms.

Stuffy nose (rhinitis) – There are very few studies in this area, but a weak link has been established between MSG ingestion and rhinitis in three patients. These results have not been repeated; therefore, not enough research has been conducted to make scientifically-informed conclusions.

Headaches/ Migraines – It is hypothesized that glutamate may interfere with acetylcholine synthesis which may be the cause of reported migraines upon consumption of foods with added glutamate. However, there have been zero clinical trials to date testing glutamate and migraine/headache symptoms specifically, so there is no in vivo evidence linking the two.

The crisis of Chinese Restaurant Syndrome wreaked havoc on the food and restaurant industries simply by the submission of one infamous letter to the editor in 1968. Immediately MSG began to be phased out, where possible, from food products which spurred research and systematic reviews of glutamate food additives. As a result of that heightened research, there is no significant evidence for harm from glutamate except in an extremely small subset of the population. In fact, research in the area has highlighted positive effects from MSG including its role in several facets of digestion and reduction of sodium in foods at levels up to 30-40%.

In a time of hypersensitivity toward food additives, the story surrounding MSG’s stigma should be a cautionary tale to not rush to judgment before banning certain ingredients from your diet. Always read articles (including this one) from a critical point of view. And look to the scientific literature rather than an opinion on the safety of a particular food ingredient.

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Kelsey is originally from Minnesota and received her B.S. in Food Science from Purdue University. Most recently, she attained an M.S. in Food Science from Penn State where her research focused on mitigating the taste of bitter for pediatric medications. She lives in New York as a confectionery technologist (candy product development = dream job!). Kelsey loves eating cookie dough by the spoonful, collecting cookbooks, and watching old episodes of Top Chef. You can follow along with her adventures in the kitchen on her blog Appeasing a Food Geek! (Follow her on Twitter! @Kelsey_Tenney)