The ketogenic diet, more commonly referred to as the “keto diet”, is one of the most popular diets for weight loss right now. This very low carb eating plan promises rapid and dramatic weight loss to its followers. However, medical experts remain dubious about its safety and efficacy. So are the keto diet and phentermine a good combination? Here we’ll discuss the keto diet: its origins, pros & cons, and the advisability of combining phentermine and low carb or fad diets.
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What is the keto diet?
The popular keto diet is a very low carbohydrate, moderate protein, high fat diet. There are several variations of this latest fad diet, but the “standard” keto diet calls for a distribution of 75% fat, 20% protein and 5% carbs. This means that just 5% of daily calories come from carbs – that’s just 75 calories (about 19g of carbs) for a person eating 1500 calories per day!
Other variations of the keto diet include the high-protein ketogenic diet (60% fat, 35% protein, 5% carbs), cyclical ketogenic diet (5 days on, 2 days off) and targeted ketogenic diet (eat more carbs around workouts). The last two are primarily designed for athletes have not been extensively studied (1).
However, not everyone needs to restrict carbs quite this much. Many people can achieve a state of ketosis by eating anything less than about 50 grams of net carbs (total grams of carbs – total grams of fiber) per day. Other low-carb diets that are still colloquially referred to as “keto” allow for still higher levels of daily carbohydrate.
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Origins of Keto
The ketogenic diet was originally developed as a treatment for refractory pediatric epilepsy: seizure disorders in children that aren’t successfully controlled by medications. Since this diet forces the brain to shift towards using ketone bodies (from fat) instead of glucose (from carbs) as its primary energy source, adhering to a keto diet can help reduce seizure frequency and severity.
The strictest clinical patients follow a 4:1 keto diet wherein they get 80% of calories from fat (ideally MCTs, which are more ketogenic) and only 20% of calories from protein & carbohydrates. The clinical goal of this diet is to provide just enough protein and calories to support sufficient growth and weight status, while absolutely limiting carbohydrate intake to reduce epileptic symptoms.
Medically, epilepsy management remains the only widely-accepted use of the ketogenic diet. However, scientists are researching the diet’s potential effectiveness in treating or managing other neurological disorders and cancer (2).
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How It Works
The basic idea behind the keto diet is to drop your intake of carbohydrates so low that your body and brain switch to ketone bodies as their main source of fuel.
Fueling Your Body on a Balanced Diet
Under normal conditions, the body relies on glucose as its primary source of energy.
Glucose, or sugar, is the most biologically-available source of fuel and it’s our brain’s favorite food. When we’re eating a normal, balanced diet about 50-60% of our calories come from carbs. Grains, fruits, vegetables (especially starchy vegetables like potatoes, corn and peas) and dairy products contribute to your daily carbohydrate intake. Sugar – whether it’s white sugar, brown sugar, honey, maple syrup or agave – is also digested as a simple carbohydrate.
When we ingest carbs, we use insulin to break down sugars in our foods and convert it them into glucose that our cells can use for energy. This is how someone eating a balanced diet gets most of their energy. The quick turnaround of glucose metabolism is why it’s normal to feel energized right after eating and then begin to feel sluggish a few hours after you eat.
Fueling Your Body on Keto
However, when the body doesn’t receive enough calories or carbs (or can’t use them because of a condition like diabetes), the liver starts making ketone bodies to fuel the body and brain. These molecules, which form from fatty acids, serve as an efficient fuel substitute for the missing glucose (3).
Traditionally, ketone tests and keto strips determine if a person is in ketosis by measuring the levels of ketone bodies in their blood, breath or urine. However, new technology (like the Ketyo) allows you to test with a simple puff of air – similar to breathing into a breathalyzer.
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Benefits of Keto
Proponents of the keto diet note many possible advantages of following this diet. The most-touted benefits are rapid & dramatic weight loss and lower insulin levels over the short-term.
Adopting a ketogenic diet allows followers to lose weight quickly and without counting calories. Many people report they feel less hungry while in ketosis, especially after the initial transition period.
Moreover, recent studies show that adults lose more weight following a high-fat/low-carb diet instead of a low-fat diet (4,5). Experts, however, note that much of this initial weight loss is simply water weight due to the drop in glycogen.
One small study (of 12 people) also indicated that the ketogenic diet could reduce insulin sensitivity. This effect would reduce risk for developing type 2 diabetes and contribute to the management of several other conditions like metabolic syndrome and PCOS (6).
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Possible Risks of Keto
The long-term side effects of using ketosis for weight loss have not been studied, nor has the combination of the keto diet and phentermine weight loss pills. Health experts warn that for some people the restrictive plan may do more harm than good.
Common side effects of the keto diet include constipation and dehydration (two problems already experienced by many phentermine users), as well as electrolyte and micronutrient deficiencies. A low carb, high fat diet may also increase the risk of kidney stones (especially worrisome for Qsymia users), gallbladder problems, bone fractures and/or menstrual irregularities (3).
Studies show that children who follow keto diets long-term (for seizure control) also have higher total cholesterol and LDL (bad cholesterol) levels. While keto proponents claim this diet improves heart health, long-term research indicates that it actually worsens patients’ lipid profiles.
Ketosis can also impede muscle development, including in the heart. The heart is the most important muscle in the body and you don’t want to weaken this vital organ, especially while taking a stimulant like phentermine (7).
Do NOT start a low-carb or ketogenic diet if you are taking Qsymia (phentermine HCL + topiramate-ER). Topiramate should not be combined with any sort of high-fat, low-carb diet like Atkins or keto (8).
Keto Diet and Phentermine
Many patients, and even doctors, see keto as an effective weight loss strategy during phentermine treatment. This trendy diet has helped millions of people lose weight and aligns with popular advice to eat fewer carbs and less sugar.
However, very low carb/high fat diets may not be safe for everyone and there is no research to establish the advisability of combining phentermine and keto.
Always speak with your doctor before undertaking any major dietary or lifestyle changes, including combining the keto diet and phentermine.
Here are three reasons NOT to combine the keto diet and phentermine:
1. The interaction between phentermine and keto remains unknown
Evidence does not yet support the keto diet as an alternative or addition to phentermine. Moreover, researchers do not know about the safety or long-term effects of using ketosis for weight loss.
NEVER follow keto, Atkins, or any other low-carb/high-fat diet while taking Qsymia.
2. Strict keto isn’t a sustainable dietary pattern for most people
The most effective diets for weight loss are the ones we can stick to long-term. Very few people maintain a super-restrictive eating plan like keto for years at a time and, in most cases, the weight comes back as soon you start eating normally again.
3. Keto undermines development of healthy habits
Phentermine is a powerful appetite suppressant, but it’s ultimate purpose is to help you establish long-term lifestyle changes. As a result, it’s important to use your three months on phentermine to establish healthier eating and exercise habits that you can maintain long-term.
If you still want to eat low-carb or follow keto while taking phentermine, discuss it with your doctor and dietitian first. They can help you develop an individualized, healthy plan for weight loss.
Go into your appointment prepared with a individualized plan for weight loss with keto! Click here to see your easy, 7-day plan
Do you use the keto diet and phentermine together? Share your questions and comments with us in the comments section below!
- R. Mawer, “The Ketogenic Diet 101: A Detailed Beginner’s Guide,” 17 Jun 2017. [Online]. Available: https://www.healthline.com/nutrition/ketogenic-diet-101.
- Wikipedia, “Ketogenic diet,” 11 May 2018. [Online]. Available: https://en.wikipedia.org/wiki/Ketogenic_diet.
- S. Fan, “The fat-fueled brain: unnatural or advantageous?,” 1 Oct 2013. [Online]. Available: https://blogs.scientificamerican.com/mind-guest-blog/the-fat-fueled-brain-unnatural-or-advantageous/.
- B. Brehm, R. Seeley, S. Daniels and D. D’Alessio, “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.,” Journal of Clinical Endocrinology & Metabolism, pp. 1617-23, 2003.
- N. Bueno, I. de Melo, S. de Olivera and T. da Rocha Ataide, “Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials.,” The British Journal of Nutrition, pp. 1178-87, 2013.
- G. Boden, K. Sargard, C. Homko, M. Mozzoli and T. Stein, “Effect of a low-carbohydrate diet on appetite, blood glucose levels, and insulin resistance in obese patients with type 2 diabetes.,” Annals of Internal Medicine, pp. 403-11, 2005.