Other issues of Nutrition Advisor

Thinking about going low-carb?

The holidays are just around the corner and many will make a New Year's resolution to lose weight. Perhaps you've been thinking about eliminating carbohydrates from your diet? With all the controversy, you may be wondering if a "low-carb" diet is safe and if it really works.

What exactly is a carbohydrate?
A carbohydrate is a nutrient whose main function is to supply energy to the body. When a food containing carbohydrate is eaten and digested, most of it is turned into the simplest carbohydrate unit, glucose, which enters the bloodstream to be used as the body's main fuel. Simply, it keeps your body running throughout the day. Sugars, starches and fiber are the three main types of carbohydrate obtained from foods.

Simple carbs
Sources of sugar, often called “simple” carbohydrates, include fruit, milk and table sugars. Whole fruits are an excellent source of simple carbohydrate because they provide quick energy, fiber and vitamins. Refined and processed sugars (sugar, soda and candy) give carbohydrates a bad name as they don't offer any of the minerals and vitamins necessary for good health and are loaded with calories.

Complex carbs
Potatoes, rice, pasta, bread, cereals and some vegetables (like squash, sweet potatoes and peas) are rich in starch and are often referred to as "complex" carbohydrates. Only certain foods high in starch provide a significant amount of dietary fiber, the indigestible part of plant foods. Fiber is beneficial because it slows down how quickly foods convert into glucose and it can help you feel less hungry during the day. Examples of high fiber starches include bran and oatmeal cereals, dried beans, lentils and some whole grain breads. Foods high in starch can be high in calories when they are eaten in large portions or if they are prepared with high fat oils or toppings.

Insulin resistance
The reason why carbohydrates have become the “bad guy” is because the pancreas releases insulin when they are eaten in order to metabolize the glucose created. Some scientists believe that excess carbohydrate consumption leads to chronically elevated levels of insulin in the bloodstream. Over time, the body does not use the insulin properly and a state of insulin resistance develops. Medical conditions such as obesity, hypertension, high blood triglyceride levels and diabetes have all been linked to insulin resistance. By comparison, the pancreas secretes very little insulin in response to dietary proteins and fats.

Impact of a low-carb diet
Recent research shows that people who eliminate carbohydrates from their diet and replace them with proteins and fats (like cheeseburgers, bacon, cheese and butter) are effective at losing weight—at least in the short run. But what happens later? No one really knows the answer because the long-term effects of eliminating carbohydrates from the diet have yet to be fully investigated. Some researchers point out that the weight loss achieved on these types of diets can be due to an overall restricted caloric intake rather than solely eliminating carbohydrates.

Ketosis
If a high protein diet is extremely low in carbohydrates, a state of ketosis can occur and body fat breaks down very quickly. While this may sound appealing, it increases the risk of gout, kidney and liver problems, electrolyte abnormalities, dehydration and bad breath. Further, ketosis is very dangerous during pregnancy and for individuals with diabetes. Since high-carbohydrate diets that restrict calories produce weight loss as well, the researchers go on to say that there is currently no definitive evidence to recommend for or against the use of low-carbohydrate diets.

Is a low-carb diet a healthy way to lose weight?

Benefits

• Quick weight loss can be motivating
• Some feel less hungry throughout the day
• Eliminates “empty calories” from sugar in the diet
• May help decrease glucose levels
• Diet has clear guidelines to follow

Potential consequences

• Ketosis
• Rapid weight gain once diet is stopped
• Some feel tired, hungry, dizzy or nauseous
• High saturated fat and cholesterol intakes can raise blood cholesterol levels
• Diet involves minimal fiber causing constipation and long-term risk of cancer
• Diet is poor in calcium and vitamins A & C
• Foods are expensive to purchase

Our advice
Eliminating carbohydrates from your diet and replacing them with fats and protein may not cut your calorie intake and this is essential for weight loss. To lose weight:

• Choose a well-balanced diet that incorporates high fiber carbohydrates, lean proteins and unsaturated fats.
• Control portion sizes and begin an exercise plan. You will be more likely to keep the weight off in the long run, without harming your body. Always talk to your doctor before starting any diet or exercise plan.

If you decide to follow a high protein, low carbohydrate diet, here are some tips to keep in mind:

• Choose the leanest protein sources (baked fish, skinless chicken, low fat cheese).
• Take a multiple vitamin, and some may need calcium supplements.
• Don't eliminate all carbohydrates. Include vegetables, whole fruits and high fiber starches such as dried beans, lentils and bran or oatmeal cereals in your daily diet.
• Use unsaturated fats like olive or canola oil and nuts, instead of animal fats like butter or bacon.

The Yale-New Haven Nutrition Advisor is created by registered dietitians and dietetic interns who staff the Nutrition Clinic at Yale-New Haven Hospital. For information, contact the Nutrition InfoLine at (203) 688-2422.

For more information on this topic, you could visit:

• Statement on high-protein, low-carbohydrate diet study presented at scientific sessions, American Heart Association, November 19, 2002
• Nutrients and normal blood sugar control, Yale New Haven Health Library
• Heart association warns against high protein diets, Yale-New Haven HealthLINK, November 21, 2001
• Ketones, Yale New Haven Health Library
• Low carbohydrate diets, Quackwatch, July 29, 2003
• Nutrition for healthy living, Yale-New Haven Hospital

Other issues addressed by Yale-New Haven Nutrition Advisor:

• What's to drink?
• Obesity—it's not just for grown-ups anymore
• Fruits and vegetables: Always in season
• Calcium: Not just for bones anymore!
• Mercury Rising
• A powerful B vitamin: Folate
• Vegging out
• Manic for organic
• Beta carotene
• Shellfish & cholesterol
• Sorting through nutrition information
• Summer fruit sensations
• Make it fun in the sun (outdoor food safety tips)
• Archive

Last revised: March 10, 2005 (jj)

Home page URL: http://www.ynhh.org

All information is intended for your general knowledge and is not a substitute for medical advice or treatment for specific medical conditions. You should seek prompt medical care for any specific health issues and consult your physician before starting a new fitness regimen.