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Keto Diet


Kelsey is a member of the care team at the Weight and Wellness CenterLauren Fialkoff, MS, RDN, LDN is a Clinical Bariatric Dietitian in the Weight and Wellness Center at Tufts Medical Center in Boston, MA.The ketogenic diet or "keto" has gained considerable attention as a potential weight loss strategy. Because it burns fat for energy, it is becoming more common amongst celebrities and by patients for health purposes. We asked Kelsey Kalenderian, RDN, LDN and Lauren Fialkoff, MS, RDN, LDN, clinical bariatric dietitians with the Weight and Wellness Center, to explain what ketosis is and how to best adjust this diet to fit your lifestyle.

What is ketosis?

Ketosis is a metabolic adaptation that has allowed humans to survive during periods of famine. When the body does not have enough carbohydrates to use for energy (also known as glucose or sugar) it will break down fat and this produces ketones. Ketones provide energy to the brain when carbohydrates are sparse.  When ketones accumulate in the body this is called ketosis.    

What is a ketogenic diet?

A ketogenic diet is a low carbohydrate, high fat eating pattern. The ketogenic diet recommends 70-80% of total calories come from fat with the majority of remaining calories from protein. Carbohydrate intake is restricted but can be variable; some ketogenic diets recommended carbohydrate intake as a low as 20g/day and as high as 50g/day.  Historically, the ketogenic diet was used as a treatment for epilepsy in children whose medication was ineffective. Recently, the ketogenic diet has gained considerable attention as a potential weight loss strategy by sending the body into ketosis and burning fat for energy.

Can you jump right into this diet or is there stages?

If someone is interested in starting the ketogenic diet, it is recommended to speak to a registered dietitian and/or medical professional to ensure the safety of the diet. After doing so, there are no specific stages to follow and one can “jump” right into it. However, slowly transitioning toward a ketogenic diet may increase the likelihood of sustainability.  

How effective is cutting carbs from your diet? Is it safe?

As a dietitian, I often get the question, “what is the best diet to lose weight?” And the truth is – research shows there is no one diet that will promote weight loss. The best diet to promote weight loss is one that is sustainable and easy to follow. Any diet that results in a calorie restriction, including low carbohydrate diet will result in weight loss. However, for some, cutting carbohydrates is not sustainable and results in adverse symptoms which may include hunger, low mood, constipation and headaches. It is important to consult with a medical doctor and registered dietitian to evaluate the safety of a low carb diet.

Is this diet recommended to patients for weight loss?

Current research on the ketogenic diet for weight loss is limited.  Most of the studies are small and short term. A study published in the British Journal of Nutrition concluded that participants who followed a ketogenic diet compared to a low fat diet demonstrated short term weight loss benefits. However, these results were not significant after 1 year when compared with the effects of conventional weight loss diets.

According to an article published by Harvard’s School of Public Health, there are several theories as to why the ketogenic diet may promote weight loss. These include the satiating effect associated with high fat foods which can result in decreased food cravings, a decrease in appetite-stimulating hormones due to the restriction of carbohydrate foods, an increase in energy expenditure as fat and protein are converted into glucose, and a promotion of fat loss versus lean body mass. It’s important to remember that these are theories and not necessarily facts, as they have not been consistently shown in research. 

What foods can you eat on the keto diet? 

The ketogenic diet has a strong emphasis on fat at each meal. Fatty cuts of meats, lard, avocados, plant oils and oily fish are allowed. Dairy foods such as butter and cheese may be allowed, although some dairy can be a significant source of lactose (milk sugar) such as ice cream and full fat milk. Protein intake is moderate on the diet. Most programs recommend free-range poultry and grass-fed beef, not grain fed.  In addition, pork, bacon, organ meats, eggs, tofu and certain nuts and seeds are allowed. Non-starchy vegetables such as leafy greens, cauliflower, broccoli, onions, mushrooms, summer squashes and zucchini are included in the diet. Finally, certain fruits low in sugar such as berries are allowed in small portions.

What foods should you cut from your diet?

There are many variations of the ketogenic diet, but all restrict carb-rich or starchy foods, such as bread, cereals, pastas, rice, beans and legumes, and cookies. Foods and beverages with added and natural sugars are also restricted. This includes sugars as honey and maple syrup, sugar sweetened beverages and fruit juices, and starchy vegetable such as potatoes, corn, and peas. Most versions of the ketogenic restrict intake of wines and beers, as well as drinks with added sweeteners such cocktails, mixers with syrups and juice, and flavored alcohols.  

Should other areas of the diet/habits be adjusted to still get the nutrients needed?

Since the ketogenic diet restricts intake of carbohydrates, fruits, dairy and some veggies, possible nutrient deficiencies may arise if a variety of allowed foods are not included.  It is important to eat a variety of meats, fish, veggies, fruits, nuts and seeds to ensure adequate intake of fiber, iron, magnesium, zinc and B vitamins. Specifically, many B vitamins are found in whole grains which are typically restricted on the ketogenic diet. Working with a registered dietitian can ensure that any use of the ketogenic diet minimizes potential nutrient deficiencies.