So, working as a clinical dietitian has its benefits in being able to help a very wide variety of patients, but lately I've been barraged with so many questions about the ketogenic diet. I did a previous post on the specifics of this diet and have actually been involved in helping people to get off of it (check out article in Shape Magazine).
Here's the deal: Finding a dietitian to work with is as tricky as finding the right doctor or teacher who really "gets you" and understands and supports YOUR current goals. However, just like any provider it's my ethical duty to inform you about your options and make recommendations based on scientific evidence which supports that, then let you make an informed decision from there. So regardless of what I personally feel about this ketogenic diet, here is the evidence I have found thus far:
1. The vast majority of evidence for the use of this diet for medical purposes is indicated for individuals with epilepsy and other seizure disorders or Type 1 Diabetes. The rules on this are fairly consistent about the balance of macronutrients (fat:protein:carbohydrates) and the types of fats being used (unsaturated oils like olives, canola, fish, nuts and seeds, avocados) while still paying close attention to calories since fats contain 9 calories per gram, compared to protein and carbs which each only have 4 calories per gram.
2. Related to weight loss, the results from Google Scholar are pretty varied. So I'll break it down:
- "In the short term, high-protein, low-carbohydrate ketogenic diets reduce hunger and lower food intake significantly more than do high-protein, medium-carbohydrate nonketogenic diets (American Journal of Clinical Nutrition, 2008)
- "A systematic review of low-carbohydrate diets found that the weight loss achieved is associated with the duration of the diet and restriction of energy intake, but not with restriction of carbohydrates...{the trials} showed better weight loss on the low-carbohydrate diet after 6 months, but no difference after 12 months." It continues to say "Long-term studies are needed to measure changes in nutritional status and body composition during the low-carbohydrate diet, and to assess fasting and postprandial cardiovascular risk factors and adverse effects. Without that information, low-carbohydrate diets cannot be recommended." (Systematic Review, The Lancet)
- A comparison of 4 different fad diets (Atkins-ketogenic, Zone, Weight Watchers, Ornish diets) over a 12 month span indicated that "in each diet group, approximately 25% of the initial participants sustained a 1-year weight loss of more than 5% of initial body weight and approximately 10% of participants lost more than 10% of body weight. Weight reductions were highly associated with waist size reductions for all diets (Pearson r = 0.86 at 1 year; P<.001), with no significant difference between diets." (JAMA, 2005) *The added kicker in this study is how the cardiovascular risks were impacted. Each group was encouraged to exercise, which many did several times per week and the amount of weight loss was associated with changes in exercise level REGARDLESS of which diet they were on. Also, "no diet significantly worsened any cardiac risk factor in association with weight loss or dietary adherence at 1 year."
- In another study done by the Philadelphia VA Medical Center on men with BMI >35 (that's categorized as Obese class II), the low-carb diet (30-50g daily with no specifics on how much fat or protein) compared with a conventional low-fat diet (500 calorie reduction and <30% of daily calories from fat) was more effective at reducing triglycerides and improving HgbA1c (though no numbers were provided and I would expect that both effected it) and weight loss was the same for both diets. They also corrected for weight loss but indicated that glucose sensitivity was the same with regards to improved A1c. The big thing here too is the adherence part again with a 34% dropout rate, indicating that these diets are not sustainable long-term.
On the contrast, a study from 2013 from the British Journal of Nutrition indicated that "Individuals assigned to a VLCKD achieve a greater weight loss than those assigned to a LFD in the longterm" with measurements again at 1 years time. This systematic review did look at only 5 studies which matched criteria for inclusion and had statistical significance, but it indicated also that the very-low carbohydrate ketogenic diet (VLCKD) may have beneficial impact on triglyceride levels and blood pressure without much impact on cholesterol levels.
3. The list of evidence in PubMed, Google Scholar, and Biomed Central (all great places to find research articles) on the detrimental health effects of high fat diets is overwhelming. Heart disease and stroke, type 2 diabetes, colon and rectal cancers, non-alcoholic fatty liver disease, gut disbiota, etc. Weird how the outlook changes a bit when you change a few keywords in the search, but isn't that what we're looking at here? A ketogenic diet is a very high-fat diet with minimal carbohydrate which cuts out at least 2 whole food groups: grains and fruits. Both of these groups are nutrition powerhouses with the majority of the vitamins and minerals we need in a day. The only source then for the majority of our nutrients is to eat a variety of non-starchy vegetables (no corn, peas, potatoes, or legumes) or to supplement with pills.
So, in looking at a fairly wide variety of evidence from all over the nutrition science world, I am still very confident that this is not the ultimate weight-loss savior diet it's made out to be. The best recommendation out there is still to eat a variety of foods from all 5 food groups, minimize processed foods and sugary drinks and snacks, drink lots of water, and get about 20-30 minutes of walking in per day for a healthy, lifelong non-dieting lifestyle.
Here's the deal: Finding a dietitian to work with is as tricky as finding the right doctor or teacher who really "gets you" and understands and supports YOUR current goals. However, just like any provider it's my ethical duty to inform you about your options and make recommendations based on scientific evidence which supports that, then let you make an informed decision from there. So regardless of what I personally feel about this ketogenic diet, here is the evidence I have found thus far:
1. The vast majority of evidence for the use of this diet for medical purposes is indicated for individuals with epilepsy and other seizure disorders or Type 1 Diabetes. The rules on this are fairly consistent about the balance of macronutrients (fat:protein:carbohydrates) and the types of fats being used (unsaturated oils like olives, canola, fish, nuts and seeds, avocados) while still paying close attention to calories since fats contain 9 calories per gram, compared to protein and carbs which each only have 4 calories per gram.
2. Related to weight loss, the results from Google Scholar are pretty varied. So I'll break it down:
- "In the short term, high-protein, low-carbohydrate ketogenic diets reduce hunger and lower food intake significantly more than do high-protein, medium-carbohydrate nonketogenic diets (American Journal of Clinical Nutrition, 2008)
- "A systematic review of low-carbohydrate diets found that the weight loss achieved is associated with the duration of the diet and restriction of energy intake, but not with restriction of carbohydrates...{the trials} showed better weight loss on the low-carbohydrate diet after 6 months, but no difference after 12 months." It continues to say "Long-term studies are needed to measure changes in nutritional status and body composition during the low-carbohydrate diet, and to assess fasting and postprandial cardiovascular risk factors and adverse effects. Without that information, low-carbohydrate diets cannot be recommended." (Systematic Review, The Lancet)
- A comparison of 4 different fad diets (Atkins-ketogenic, Zone, Weight Watchers, Ornish diets) over a 12 month span indicated that "in each diet group, approximately 25% of the initial participants sustained a 1-year weight loss of more than 5% of initial body weight and approximately 10% of participants lost more than 10% of body weight. Weight reductions were highly associated with waist size reductions for all diets (Pearson r = 0.86 at 1 year; P<.001), with no significant difference between diets." (JAMA, 2005) *The added kicker in this study is how the cardiovascular risks were impacted. Each group was encouraged to exercise, which many did several times per week and the amount of weight loss was associated with changes in exercise level REGARDLESS of which diet they were on. Also, "no diet significantly worsened any cardiac risk factor in association with weight loss or dietary adherence at 1 year."
- In another study done by the Philadelphia VA Medical Center on men with BMI >35 (that's categorized as Obese class II), the low-carb diet (30-50g daily with no specifics on how much fat or protein) compared with a conventional low-fat diet (500 calorie reduction and <30% of daily calories from fat) was more effective at reducing triglycerides and improving HgbA1c (though no numbers were provided and I would expect that both effected it) and weight loss was the same for both diets. They also corrected for weight loss but indicated that glucose sensitivity was the same with regards to improved A1c. The big thing here too is the adherence part again with a 34% dropout rate, indicating that these diets are not sustainable long-term.
On the contrast, a study from 2013 from the British Journal of Nutrition indicated that "Individuals assigned to a VLCKD achieve a greater weight loss than those assigned to a LFD in the longterm" with measurements again at 1 years time. This systematic review did look at only 5 studies which matched criteria for inclusion and had statistical significance, but it indicated also that the very-low carbohydrate ketogenic diet (VLCKD) may have beneficial impact on triglyceride levels and blood pressure without much impact on cholesterol levels.
3. The list of evidence in PubMed, Google Scholar, and Biomed Central (all great places to find research articles) on the detrimental health effects of high fat diets is overwhelming. Heart disease and stroke, type 2 diabetes, colon and rectal cancers, non-alcoholic fatty liver disease, gut disbiota, etc. Weird how the outlook changes a bit when you change a few keywords in the search, but isn't that what we're looking at here? A ketogenic diet is a very high-fat diet with minimal carbohydrate which cuts out at least 2 whole food groups: grains and fruits. Both of these groups are nutrition powerhouses with the majority of the vitamins and minerals we need in a day. The only source then for the majority of our nutrients is to eat a variety of non-starchy vegetables (no corn, peas, potatoes, or legumes) or to supplement with pills.
So, in looking at a fairly wide variety of evidence from all over the nutrition science world, I am still very confident that this is not the ultimate weight-loss savior diet it's made out to be. The best recommendation out there is still to eat a variety of foods from all 5 food groups, minimize processed foods and sugary drinks and snacks, drink lots of water, and get about 20-30 minutes of walking in per day for a healthy, lifelong non-dieting lifestyle.
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