Pros and Cons of the Ketogenic Diet

ketogenic diet

It doesn’t seem logical: a diet loaded with coconut oil, butter and fatty cuts of red meat will help you lose fat. What is more, your energy levels will soar through the roof, you’ll maintain better focus throughout the work day and feel fully rested all the time. A ketogenic diet seems s a radical path to potentially unbelievable results.

For almost a century, epileptic patients have used ketogenic diets to control seizures when traditional medications provide no relief. In the early 1970s, Dr. Atkins presented ketogenic diets mainstream with his book, Dr. Atkins’ Diet Revolution: The High Calorie Way to Stay Thin Forever. However, interest quickly waned as health professionals began recommending low-fat diets (especially low saturated fat) for heart health, but four decades later, interest in ketogenic diets is once again peaking.

Ketogenic diets consist of 8090% calories from fat, 15% from protein and 5% from carbohydrate or about 3-4 grams of fat for every gram of protein plus carbohydrate (combined). A person following a ketogenic diet should eat bacon, eggs, heavy cream, non-starchy vegetables, mayonnaise and sausage, and avoid breads, cereal, pasta, fruits, starchy vegetables and other carbohydrate-rich foods.

weight loss
In addition to relying on fat for energy, the ketogenic diet naturally suppresses the pathways that produce and store body fat.


During the first several days on a ketogenic diet, your body uses its limited supply of carbohydrate stored in your liver and muscle tissue. When your carbohydrate stores dwindle, you can feel tired, get headaches and find workout requires much more effort. Once this stash of energy is depleted, ketones, formed from the breakdown of dietary fat, become the primary source of fuel. It takes at least seven days to reach nutritional ketosis and a couple of weeks to fully adapt to the diet.

In addition to relying on fat for energy, the ketogenic diet naturally suppresses the pathways that produce and store body fat. Ketogenic diets may also help reduce feelings of fatigue and improve mental clarity. Animal and human studies suggest ketogenic diets as well as low-carb, high-protein, high-fat diets reduce some markers of inflammation, which some theorize may help relieve muscle soreness. Nevertheless, there’s not enough research on ketogenic diets and recovery from exercise or muscle soreness.

man and woman drinking water
You won’t be able to maintain high-intensity exercise for very long while on a ketogenic diet.


Experts say that athletes, once fully adapted to a ketogenic diet, can rely on a seemingly endless supply of body fat for energy. There’s no need for sports drinks, beans, carb gels and gummies every 15-30 minutes during long runs, rides or triathlons to maintain energy levels. Fewer calories consumed may make it easier for some people to stay within their total daily calorie requirements (however, if you are training that much, staying within your calorie needs shouldn’t be difficult).

Trading carbs for fat seems like an enormous benefit for endurance athletes, especially the ultra runner or triathlete who trains for several hours at a time. However, right now this idea is grounded in more theory than fact.

In the one true ketogenic diet study analyzing athletic endurance, researchers had subjects cycle at a snail’s pace (equivalent to a heart rate of about 120 beats per minute for anyone 20 to 30 years old or 115 for a 40-year-old) until they became exhausted before and after four weeks on a ketogenic diet. There were no differences in the amount of time they were able to cycle before getting tired prior to or after the four-week ketogenic diet.

In studies analyzing the connection between high-fat diets and endurance performance, participants relied on more fat as opposed to carbohydrate during exercise, but there was no clear performance advantage to the high-fat diet. If your main goal is weight loss, it doesn’t matter if you use more fat than carbohydrate while exercising as long as you’re burning more total calories over throughout the day. Plus, in the interest of time, you may want to ramp up the intensity and burn as many calories in a short period of time as you possibly can.

Unfortunately, a ketogenic diet won’t help you achieve that. A person may be able to maintain very low-intensity endurance exercise while following a highfat diet, but this in all probability isn’t the best strategy for those who train at a high-intensity level or athletes who compete in high-intensity sports (such as sprinting, tennis, football, soccer, basketball). You won’t be able to maintain highintensity exercise for very long while on a ketogenic diet. Converting body fat into a usable form of energy is a very slow process that demands a considerable amount of oxygen. Try getting through cardio when your body is sucking in oxygen to get your working muscles the energy they need to keep going. The higher the intensity, the faster your body needs energy.

man lifting weight
High-fat, high-protein, low-carb diets were found to result in a decreased lean body mass.

Some researchers also question whether this diet is suitable for those who want to gain mass and strength. Some experts say that the ketogenic diet decreases the number of the signalling molecules involved in muscle growth, which makes it difficult for muscles to get bigger and stronger.

A review of thirteen studies examining high-fat, high-protein, low-carb diets (containing less than 55 grams of carbs a day) found that almost all of the studies reported a decrease in lean body mass, while few reported no change or an increase. However, many of these studies were carried out to induce weight loss, and it’s known that weight loss often results in the loss of lean body mass to some extent. To complicate matters more, low-carb diets (including ketogenic diets) result in a considerable drop in carbohydrate content, and associated water stored with it, in muscle. This change overestimates the decrease in lean body mass.

Just because carb intake is low, if protein intake is high enough and includes enough essential amino acids, the pathways regulating the synthesis of new protein in muscle will be up-regulated. Can you keep your protein intake low enough (the recommended intake is  2.2g of protein per kilo of body weight)  to remain in ketosis but still high enough to build muscle? Probably. Researchers suggest more than 2.5 grams of protein per kilogram bodyweight or more than 25-30% of total daily calorie intake could suppress ketogenesis, amounts much higher than most people need to grow muscle and also higher than the traditional definition of a ketogenic diet. Each person has a different carbohydrate and protein limits to stay in ketosis and therefore, measuring ketones through blood or urine is the only definitive way to determine if you can meet your protein needs for muscle and remain in ketosis at the same time.

Some studies in athletes suggest ketogenic diets could help athletes lose or maintain weight without compromising performance. However, these studies didn’t follow a ketogenic diet protocol but instead were high-fat, high-protein, low-carb diets. All came closer to a 2:1 or 1:1 ratio of fat to protein plus carbohydrate (carb intake was kept very low, but protein intake was higher than a ketogenic diet). Also, none of the studies measured if the study subjects were actually in nutritional ketosis.

mediterranean diet
Ketogenic diets are usually low in vitamin D, calcium, magnesium, potassium, folic acid and fibre, which should therefore be supplemented.


Soon after starting a ketogenic diet, blood cholesterol levels and artery stiffness went up in epileptic children. High total and LDL cholesterol are recognized as risk factors for cardiovascular disease. Increases in artery stiffness decrease the capability of arteries to expand in response to adjustments in pressure. When arteries can’t open up as widely to accommodate blood flow, blood pressure increases, resulting in microscopic tears on artery walls, scar tissue and the perfect surface for plaque buildup.

Even though the consequences sound dire, blood cholesterol levels went back to normal in patients who stopped following the diet and in those who stayed on it, they returned to normal after 6-12 months. Likewise, artery stiffness became normal again after 24 months on a ketogenic diet. Research in obese people shows ketogenic diets improve blood glucose and blood cholesterol levels over time, either because of the diet, weight loss from the diet, a combination of the two or carbohydrate restriction.

Ketogenic diets are usually low in vitamin D, calcium, magnesium, potassium, folic acid and fibre. There are several potential consequences connected to long-term low intake of each of these micronutrients, including decreased bone density, softening of the bones, muscle weakness or spasms, muscle damage, and abnormal heart rhythm. Nevertheless, with careful planning, multivitamin and fibre supplement and under the guidance of a physician who may prescribe sodium and potassium supplements (while on the ketogenic diet, blood sodium can drop to dangerously low levels), nutrient needs can be fulfilled. Additionally, to prevent constipation when on a ketogenic diet, one should drink a lot of fluids.

low-carb diet
If you don’t want to suffer the first few days of fatigue and headaches, reduce your carb intake gradually before going on the diet.


A ketogenic diet is safe for healthy individuals when overseen by a doctor. Like many diets, the major issue is adherence—food choices are limited and there are no diet-free days. You can’t go on a ketogenic diet from Monday to Friday and then blow it out on the weekends, or decide to have bread in your sandwich and expect to reap the potential rewards of long-term adaptation to nutritional ketosis.

All or nothing. The diet works, but you have to follow it strictly. Fortunately, the more you follow ketogenic diet, the easier it gets and the more benefits you get. If you don’t want to suffer the first couple of days of fatigue and headaches, begin with a lower carbohydrate diet and wait until your body adjusts before fully adopting a ketogenic diet.

Instead of relying on high intakes of saturated fat, it’s a good idea to make this diet healthier by adopting a Mediterranean approach and incorporating fatty fish, extra virgin olive oil and lots of non-starchy very low carbohydrate vegetables.

If you follow a ketogenic diet, this probably won’t catapult you into an age class winner in your sport. What is more, it isn’t clear what effect the diet will have on the measures of strength and power as well as gains in muscle mass. However, this diet is one of multiple possible approaches to weight loss and can also improve your energy levels and mental clarity.

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Written by Camille Bennett

Camille Bennett is our nutrition expert interested in fitness diet and doesn’t run out of delicious ideas for healthy and nutritional meals.


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