Report of Health Problems on Low Carb Diets

Carbs in Food
Glycemic Index GI of Carbs
Glycemic Load of Carbs
GI Diet - Low GI Diet

Information About Carbs | Carbohydrates Guide | Low Carb Diets

4. Discussion of Health Concerns

Extract from "Updated Analysis of Health Problems Associated with High-Protein, High-Fat, Carbohydrate-Restricted Diets Reported via an Online Registry" by the Physicians Committee for Responsible Medicine (PCRM) (Dec, 2003)

Note: Numbers in brackets refer to research references. See Low Carb Eating References


Constipation was reported by 44 percent of the registrants. One registrant reported severe problems with constipation: “I frequently resorted to laxatives and sometimes went two weeks without a bowel movement.” In one study, 68 percent of subjects on a low-carbohydrate diet reported problems with constipation. (1)

Carbohydrate-rich plant foods, including vegetables, fruits, grains, and legumes, are the main sources of fiber in the diet. High-protein, carbohydrate-restricted diets are typically low in fiber, and, as a result, often lead to constipation. In our nutrient analysis of the sample menus in Dr. Atkins’ New Diet Revolution, fiber content ranged from two grams per day on the Induction Diet to 18 grams per day on the Maintenance Diet. The new Institute of Medicine recommendations target fiber intake at 14 grams per 1000 kcals, which works out to 28 to 42 grams per day for an average adult. Individuals consuming Atkins-like diets generally fall far short of this healthy goal.

Lack of Energy

Loss of energy was reported by 40 percent of registrants. One registrant noted feeling “exhausted, dizzy, and nauseated before almost passing out on the 5th day of the diet.” Another noted being “so weak I can hardly function.” A third stated, “After two weeks I felt terribly tired and ended the diet with a donut binge session.” Loss of energy would be expected on a carbohydrate-restricted diet, because the preferred fuel for the body is carbohydrate in the circulating form of glucose or the storage form of glycogen. Muscles need glucose to do maximal effort work. (19) Limiting carbohydrate intake requires the body to utilize other fuels, such as fats, amino acids, and ketone bodies. Conversion of these nutrients to useable fuels takes longer than providing glucose from carbohydrates. For brain function and high-intensity activities, these fuels are poor substitutes for glucose. In addition, during the induction and maintenance phases, recommended caloric intake (1500–1700 kcals) is well below adult energy requirements.

Bad Breath (Halitosis)

Bad breath was reported by 40 percent of the registrants. One registrant noted, “I was miserable on this diet. I had no appetite, no energy, and a terrible taste in my mouth all the time.” A second summed up her statement with, “Bad breath, funny taste in mouth, feeling lethargic...and this diet is good for you? My body didn't think so!”

Bad breath occurs on high-protein, carbohydrate-restricted diets, especially during the induction and weight-loss phases, when a ketotic state is achieved. Problems with bad breath were reported in 63 percent of patients on such diets in a study done at Duke University. (1) When fatty acids are the primary source of energy and carbohydrate is severely restricted, part of the fat particle cannot be metabolized and builds up in the fluids outside the cells. These particles are converted to ketones (an “emergency” energy source), and unused ketones are excreted in the urine and expired air, resulting in acetone-smelling breath. (16)

Lack of Concentration

Difficulty concentrating was reported by 29 percent of the registrants. One registrant described her experience this way: “I felt horrible. I couldn’t concentrate or focus and felt foggy all the time.” Another stated, “I was only on the diet a short time and had a vertigo attack. I have since been out of balance and have a loss of concentration.”

The primary fuel for the brain and nervous system is carbohydrate in the form of glucose. When carbohydrate or total food intake is restricted (especially when such restriction is <40 g/day), there is little or no glucose available for the brain. The brain cells can utilize ketone bodies for energy in an emergency, such as starvation or severe carbohydrate restriction, (20) but some individuals can still note the deficiency of glucose available to the brain. Possible symptoms include difficulty concentrating or light-headedness.

INDEX to PCRM Low Carb Health Problems Report


The PCRM Report:

Carbohydrates Definition
Carbohydrates Information
Complex Carbs Guide
Simple Carbs Guide
Starch/Starchy Carbohydrates
Sugars Carbohydrates
Carb Counting Guide
Facts About Carbohydrates
Diabetes, Carbs and Diet

Fiber in Diet
Dietary Fiber
Types of Fiber
Best Sources of Fiber
Benefits of Fiber
Daily Fiber Needs

Nutrition & Carbohydrate
Nutrition in Carbs
Minerals in Carbohydrates
Vitamins in Carbohydrates
Phytochemicals in Carbs

Carbs and Glycemic Index
Digestion of Carbs
Blood Glucose Levels
Glucose into Energy
What is Glycogen?
How is GI Measured?
What Affects Glycemic Value?
Glycemic Index Food Chart
Glycemic Index Food Pyramid
Glycemic Value of a Meal
GI Values in Carbohydrates
GI Value For Beans
GI Value For Bread
GI Value For Cereal
GI Value For Dairy Food
GI Value For Drinks
GI Value For Fruit
GI Value For Meat/Fish
GI Value For Nuts
GI Value For Snacks
GI Value For Starchy Carbs
GI Value For Sugar
GI Value For Vegetables
GI Value For Whole Grains

Carbohydrate in Foods
Atkins Diet Foods
Energy Bars
Flour/Baking Foods
Ice Cream
Milk, Cream,Yogurt

Carbs in Food cont/
Soy Food
Zone Diet Foods

Diet Recipes
GI Diet Recipes
Low Carb Recipes

Carb-Controlled Diets
Atkins Diet
South Beach Diet
Zone Diet
Low Carb Dieting
Benefits of Low Carb Diets
Low Carb Diets Health Risks
Ketosis - High Ketones in Blood
Gluconeogenesis Guide
Free Low Carb Diet Advice
Low Carb Weight Loss Diet

Diabetes, Insulin, Obesity
Diabetes Information
Hyperglycemia - High Blood Glucose
Hypoglycemia - Low Blood Glucose
Obesity Information
Diabesity, Diabetes and Obesity
Insulin Information
Insulin and Obesity
Types of Insulin
Hyperinsulimia - High Insulin Levels
Insulin Resistance Syndrome provides general information about different types of carbohydrate, like monosaccharides, disaccharides, oligosaccharides, polysaccharides, as well as nutritional value of carbohydrates, carb-content of foods, plus details of GI values of all food groups, plus advice about diabetes, impaired glucose tolerance and insulin resistance. But no information is intended as a substitute for medical advice. Copyright 2003-2021.