Social media is rampant with ketogenic diets and diet products. Walk into a health food store or your local Walmart and you will see all kinds of keto and no-carb products. Just because keto, low carb, and a no-carb diet is a trend doesn’t mean that it will work for you. In this blog post, I'll go over some studies authored by very reputable healthcare professionals studying the role of carbohydrates in various diets. You will be surprised at some of the results of the studies. Those results can help you make an informed decision about the role that carbohydrates and macro-nutrients have in your current diet. Recommendations have changed over the last few years with the number of carbs that should be eaten. I recommend that you talk to a registered dietitian if you are considering making changes to your diet especially if you have cardiovascular disease, a metabolic disease, or a health risk factor that you are concerned about. Public health officials, healthcare professionals, and health media all have conflicting information.
The 2018-2020 Dietary Guidelines for Americans suggest that Americans limit added sugars in their diet and choose whole grains rather than refined grains (HHS & DOA 2015). The Recommended Dietary Allowance for carbohydrates is 130 grams/day (IOM 2006). Neither guideline recommends a high fat intake. The American Heart Association put out a statement in 2016 stating that added sugars should be limited and most grain servings should be whole grains not refined. (Van Horn L., et al. 2016). Proper carbohydrate intake is completely different with athletes participating in sports. An athlete's needs are entirely different, especially when taking into consideration the type of exercise, the duration of exercise, the intensity and various individual factors (Thomas, Erdman, & Burke 2016). Notice that none of the organizations above are against carbohydrates. They also don't advocate a high fat intake either.
Taking a look at consumer trends and health media, it probably comes as no surprise that a lot of health trends advocate low carb diets. Registered dietitians report that one of the top trends is the ketogenic diet. The ketogenic diet offers low carb or no-carb diets. The principle behind a ketogenic diet is that your intake of carbs is so low that your body starts to convert fat for fuel. That fuel is needed for your brain and nervous system. Social media is rampant with keto recipes, low carb eating tips, before and after pictures showing drastic weight changes, personal testimonials, etc all giving support for reducing carbohydrate intake. The paleo diet is another popular diet that has been around for the past several years. Just like the many forms of low carb diets, there are many forms of paleo as well. Most of the diets have eliminated grains, dairy, and legumes.
The scientific community is exploring the pros and cons of low carb dieting related to weight control, metabolic and cardiovascular diseases. There are conflicting findings in these studies. There have been several clinical trials of low carb diets that have shown positive results with lipid profiles. Other trials have found negative effects on LDL (bad) cholesterol levels and other markers of cardiovascular health. Data of some studies do support that drastically reducing carbohydrate intake can help control blood glucose better and decrease the risk of diabetes. There has been evidence that does show a low carb diet does promote weight loss and sometimes the weight loss can happen quickly. An important note to consider with this finding is that typically a low carb diet is not any better than other caloric restricted diets over the long haul.
Below are some of those studies that have conflicting results:
A study in The Journal of Clinical Endocrinology & Metabolism found that a very low carbohydrate diet was more effective than a low-fat diet. This was only in the short term, however. There were no adverse effects on cardiovascular risk factors in healthy women after 6 months. (Brehm, B.J., et al. 2003).
A 12-month weight loss study that was published in JAMA found that there was no difference between a healthy low-carb diet and a healthy low-fat diet concerning weight loss or metabolic changes (Gardner, C.D., et al. 2018).
A study in the British Journal of Nutrition reported that a low carb diet high in protein and high in fat had a negative effect on arterial wall function in patients with increased risk of CVD. (Merino, J., et al. 2013).
A 12-month randomized clinical trial in the American Journal of Clinical Nutrition compared weight loss and glycemic control in people that have type 2 diabetes. The trial tested two groups. One group was a very low carbohydrate diet that was high in unsaturated fats and low in saturated fats. The other group was a high carbohydrate group but was low in fat. Both diets showed substantial weight loss and improvements in their blood sugar levels. The low carb group showed better improvements in blood lipid profiles, stable blood sugars and a reduction in diabetes medication. (Tay, J., et al. 2015).
A 2-year study in the New England Journal of Medicine studied moderately obese individuals on the Mediterranean diet, low-fat diet, and a low carb diet. The Mediterranean and low carb diet group both promoted weight loss and had better metabolic benefits than the low-fat diet group. (Shai, I., et al. 2008).
A meta-analysis study raised concerns with the beneficial changes of a low carb diet that showed increased levels in LDL cholesterol. This study showed a low carb diet had greater weight loss but an increased LDL cholesterol than a low-fat diet. The authors of this particular study noted that the beneficial weight loss changes from the low carb diet need to be weighed against the potential to have increased LDL cholesterol. (Mansoor, N., et al. 2016).
A review that was published in the European Journal of Nutrition in 2018 provided some insight into the low carb controversy. There is a lack of data supporting long term efficacy, safety and health benefits of low-carb, high-fat diets. People who are at high risk of developing type 2 diabetes can slow the progression of the disease if they practice lifestyle interventions with a low carb or high carb diet. Many people have difficulty in maintaining a ketogenic diet. People seem to have less difficulty in keeping 100- 150 grams of carbohydrates a day. This could be more practical in maintaining a diet for a longer period of time.
Brehm, B.J., et al. 2003 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. The Journal of Clinical Endocrinology & Metabolism, 88 (4), 1617–23
Brouns, F. 2018. Overweight and diabetes prevention: Is a low-carbohydrate-high-fat diet recommendable
Gardner, C.D., et al. 2018. Effect of low-fat vs low-carbohydrate diet on 12-month weight loss in overweight adults and the association with genotype pattern or insulin secretion: The DIETFITS randomized clinical trial. JAMA, 319 (7), 667–79
(HHS & DOA 2015). (U.S. Department of Health and Human Services and U.S. Department of Agriculture). 2015. 2015–2020 Dietary Guidelines for Americans, 8th ed. Accessed Apr. 5, 2019: health.gov/dietaryguidelines/2015/guidelines/.
IOM (Institute of Medicine). 2006. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington, D.C.: The National Academies Press
Mansoor, N., et al. 2016. Effects of low-carbohydrate diets v. low-fat diets on body weight and cardiovascular risk factors: A meta-analysis of randomized controlled trials. British Journal of Nutrition, 115
Merino, J., et al. 2013. Negative effect of a low-carbohydrate, high-protein, high-fat diet on small peripheral artery reactivity in patients with increased cardiovascular risk. British Journal of Nutrition
Shai, I., et al. 2008. Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet. New England Journal of Medicine
Tay, J., et al. 2015. Comparison of low- and high-carbohydrate diets for type 2 diabetes management: A randomized trial. American Journal of Clinical Nutrition, 102
Thomas, D.T., Erdman, K.A., & Burke, L.M. 2016. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance. Journal of the Academy of Nutrition and Dietetics
Van Horn L., et al. 2016. Recommended dietary pattern to achieve adherence to the American Heart Association/American College of Cardiology (AHA/ACC) Guidelines: A scientific statement from the American Heart Association. Circulation, 134 (22), e505–29.
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