Adopting a low-carb diet means making big changes. While more than half of the calories consumed in a standard American diet come from carbohydrates -- mainly grains, flours, starchy vegetables and sugar -- a low-carb diet limits your daily carb intake to less than 150 g a day, according to MayoClinic.com, and sometimes to less than 50 g a day. This level of carbohydrate intake corresponds to less than 30 percent, and even less than 10 percent in some cases, of your calories. This is a significant dietary change that can definitely impact some of your lab results. Before switching to a low-carb diet, first consult your doctor and get some baseline blood work done to evaluate how your dietary changes affect your results.
Triglycerides
Triglycerides are a type of fat circulating in your blood, and high levels are associated with an increased risk of heart disease. Levels below 150 mg/dL are considered desirable to keep your heart healthy, according to MayoClinic.com. In a study, obese and hyperlipidemic participants were assigned to either a low-carb or a low-fat diet. After 24 weeks, the low-carb group lowered their triglycerides by 74.2 mg/dL, while the low-fat group lowered their levels by 27.9 mg/dL, according to a study published in 2004 in "Annals of Internal Medicine."
HDL Cholesterol Levels
HDL cholesterol levels are measured when testing your lipid profile. An HDL cholesterol level above 50 mg/dL is recommended and above 60 mg/dL is even better, according to MayoClinic.com. Low-carb diets can help raise your HDL cholesterol -- considered good for heart health -- as shown in the study published in "Annals of Internal Medicine." In this study, HDL cholesterol levels increased by 5.5 mg/dL in the low-carb group, but decreased by 1.6 mg/dL in the low-fat group.
LDL Cholesterol Particle Size
LDL cholesterol levels are usually not affected significantly by a low-carb diet. After 24 weeks of following a low-carb, high-fat diet, LDL cholesterol levels increased by 1.6 mg/dL, which is not considered significant, while they slightly decreased by 7.4 mg/dL in the low-fat group. Although low-carb diets do not significantly affect your LDL cholesterol levels, they can change the size of LDL particles. Reducing your carbohydrate intake is associated with a change from small, dense LDL particles, which are considered more atherogenic, which means that it promotes plaque build-up in your arteries, to larger and fluffy LDL particles, which are less dangerous for your heart, as explained in the August 2005 issue of "Nutrition & Metabolism."
Blood Sugar Levels
Your fasting blood sugar levels as well as your hemoglobin A1C levels, which reflects your average blood sugar levels over a period of about three months, can be decreased by following a low-carb diet. In a study of patients with type 2 diabetes, those following a low-carb diet for a period of 44 months reduced their A1C levels from a baseline level of 8 percent down to 6.8 percent, as published in the May 2008 issue of "Nutrition & Metabolism." The target for hemoglobin A1C in type 2 diabetics is 7 percent or less, while healthy adults without diabetes should have an A1C result between 4.5 percent and 6 percent.
References
- MayoClinic.com: Low-Carb Diet
- MayoClinic.com: Cholesterol Levels: What Numbers Should You Aim For?
- "Annals of Internal Medicine"; A Low-Carbohydrate, Ketogenic Diet versus a Low-Fat Diet To Treat Obesity and Hyperlipidemia; William S. Yancy Jr., et al.; January 2010
- "Nutrition & Metabolism"; The Case for Not Restricting Saturated Fat on a Low Carbohydrate Diet; Jeff S. Volek, et al.; August 2005
- "Nutrition & Metabolism"; Low-Carbohydrate Diet in Type 2 Diabetes: Stable Improvement of Bodyweight and Glycemic Control During 44 Months Follow-Up; Jörgen V. Nielsen and Eva A. Joensson; May 2008
- MayoClinic.com: A1C Test
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