There are two major forms of diabetes:

  • Type 1, previously called insulin-dependent diabetes mellitus (IDDM) or juvenile-onset diabetes.
  • And type 2, previously called non-insulin-dependent diabetes mellitus (NIDDM) or adult-onset diabetes.

There are other forms of diabetes that account for about 1 out of every 20 people with diabetes.

Both type 1 and type 2 diabetes share one central feature: elevated blood sugar (glucose) levels due to a deficiency of or resistance to insulin, a hormone produced by the pancreas. Insulin is a key regulator of the body’s metabolism.

The main components (macronutrients) of food are fat, protein, and carbohydrates. Carbohydrates are primarily what affect blood glucose levels. During and immediately after a meal, digestion breaks carbohydrates down into sugar molecules (of which glucose is one) and proteins into amino acids.

  • Right after the meal, glucose and amino acids are absorbed directly into the bloodstream, and blood glucose levels rise sharply. (Glucose levels after a meal are called postprandial levels.)
  • The rise in blood glucose levels signals important cells in the pancreas, called beta cells, to secrete insulin, which pours into the bloodstream. Within 10 minutes after a meal, insulin rises to its peak level.
  • Insulin then enables glucose to enter cells in the body, particularly muscle and fat cells. Here, insulin and other hormones direct whether glucose will be burned for energy or stored for future use. Insulin is also important in telling the liver how to process glucose.
  • When insulin levels are high, the liver stops producing glucose and stores it in other forms until the body needs it again.
  • As blood glucose levels reach their peak, the pancreas reduces the production of insulin.
  • About 2 to 4 hours after a meal both blood glucose and insulin are at normal levels, with insulin being slightly higher than before the meal. When talking with your provider the blood glucose levels before another meal (e.g., after breakfast but just before lunch) are then referred to as preprandial blood glucose concentrations. The term fasting blood glucose usually refers only to the blood sugar early in the morning before breakfast when you have not eaten all night or for at least 8 hours.

In type 1 diabetes, the pancreas does not produce insulin. Onset is usually in childhood or adolescence, but can occur in adults. Type 1 diabetes is considered an autoimmune disorder meaning your own immune system is involved in causing the disease.

People with type 1 diabetes need to take insulin. Dietary control in type 1 diabetes is very important and focuses on balancing food intake with insulin intake and energy expenditure from physical exertion. Only about 5% of people with diabetes have type 1 diabetes.

Type 2 diabetes is the most common form of diabetes, accounting for about 90% of people with diabetes. In type 2 diabetes, the body does not respond normally to insulin, a condition known as insulin resistance, which means your body needs to make more insulin to achieve the same control over blood sugar levels. Over time, your ability to make high levels of insulin decreases and then type 2 diabetes develops. In type 2 diabetes, the initial effect is usually an abnormal rise in blood sugar right after a meal (called impaired glucose tolerance OR postprandial hyperglycemia).

People whose blood glucose levels are higher than normal, but not yet high enough to be classified as diabetes, are considered to have prediabetes (also called impaired fasting glucose). It is very important that people with prediabetes control their weight to stop or delay the progression to diabetes.

Obesity is common in people with type 2 diabetes, and this condition appears to be related to insulin resistance. The primary dietary goal for overweight or obese people with type 2 diabetes or pre-diabetes is weight loss and maintenance. With regular physical activity and diet modification programs, many people with type 2 diabetes can minimize or even avoid medications. Weight loss medications or bariatric surgery may be appropriate for some people. Most people only need to lose 5% to 10% body weight to cause a big improvement in control of their blood sugar level.

Lifestyle changes of diet and exercise are extremely important for people who have prediabetes, or who are at high risk of developing type 2 diabetes. Lifestyle interventions can be very effective in preventing or postponing the progression to diabetes. These interventions are particularly important for overweight or obese people. Even moderate weight loss can help reduce diabetes risk.

The American Diabetes Association recommends that people at high risk for type 2 diabetes lose weight (if necessary), engage in regular physical exercise, and follow a diet with reduced calories and lower dietary fat. High-fiber (14 grams fiber for every 1,000 calories) and whole-grain foods are recommended for prevention. These strategies can help reduce type 2 diabetes risk.

People who are diagnosed with diabetes need to be aware of their heart health nutrition and, in particular, controlling high blood pressure and cholesterol levels.

Nutrition Treatment Goals

For people who have diabetes, the treatment goals for diabetes diet are:

  • Achieve near normal blood glucose levels. People with type 1 diabetes and people with type 2 diabetes who are taking insulin or oral medication (particularly sulfonylureas) must coordinate calorie intake with medication or insulin administration, exercise, and other variables to control blood glucose levels while avoiding low blood sugar.
  • Protect the heart and aim for healthy lipid (cholesterol and triglyceride) levels and control of blood pressure.
  • Achieve and maintain reasonable weight. Overweight and obese people with type 2 diabetes should aim for a diet that controls both weight and glucose. A reasonable weight is usually defined as what is achievable and sustainable, and helps attain normal blood glucose levels. The goal for a healthy weight is a BMI <25. Children, pregnant women, and people recovering from illness should be sure to maintain adequate calories for health.
  • Delay or prevent complications of diabetes.

Nutrition Guidelines

The American Diabetes Association’s nutritional guidelines recommend:

  • The American Diabetes Association no longer advises a uniform ideal percentage of daily calories for carbohydrates, fats, or protein for all people with diabetes. Rather, these amounts should be individualized, based on your unique health profile.
  • Choose carbohydrates that come from vegetables, whole grains, fruits, beans (legumes), and dairy products. Avoid carbohydrates that contain excess added fats, sugar, or sodium.
  • Choose “good” fats over “bad” ones. The type of fat may be more important than the quantity. Monounsaturated (olive, peanut, and canola oils; avocados; and nuts) and omega-3 polyunsaturated (fish, flaxseed oil, and walnuts) fats are the best types of fats. Avoid unhealthy saturated fats (red meat and other animal proteins, butter, lard) and trans fats (hydrogenated fat found in snack foods, fried foods, commercially baked goods).
  • Choose protein sources that are low in saturated fat. Fish, poultry, legumes, and soy are better protein choices than red meat. Prepare these foods with healthier cooking methods that do not add excess fat: Bake, broil, steam, or grill instead of frying. If frying, use healthy oils like olive or canola oil.
  • Try to eat fatty fish, which are high in the omega-3 fatty acids DHA and EPA, at least twice a week. Salmon, herring, trout, and sardines are some of the best sources of DHA; sardines typically contain the highest amount.
  • Limit intake of sugar-sweetened beverages including those that contain high fructose corn syrup or sucrose (soda, juice, sports drinks). They are bad for your waistline and your heart.
  • Sodium (salt) intake should be limited to 2,300 mg/day or less. People with diabetes and high blood pressure may need to restrict sodium even further. Reducing sodium can lower blood pressure, protect the kidneys, and decrease the risk of heart disease and heart failure.

Eating Plans

There is no such thing as a single diabetes diet. People should meet with a professional dietitian to plan an individualized diet within the general guidelines that takes into consideration their own health needs.

For example, a person with type 2 diabetes who is overweight and insulin resistant may need to have a different carbohydrate-protein balance than a thin person with type 1 diabetes in danger of kidney disease. Because regulating diabetes is an individual situation, everyone with this condition should get help from a dietary professional in selecting their best diet.

Recommended eating plans include Mediterranean, vegetarian, and lower-carbohydrate diets. (Vegetarian diets can be tricky to balance because vegetarian protein sources contain carbohydrates while animal protein sources do not.) However, there is no evidence that one plan is better than another.

What is most important is to find a healthy eating plan that works best for you and your lifestyle and food preferences. Whatever diet plan you follow, try to eat a variety of nutrient-rich food in appropriate portion sizes.

Several different dietary methods are available for controlling blood sugar in type 1 and insulin-dependent type 2 diabetes:

  • Diabetic exchange lists (for maintaining a proper balance of carbohydrates, fats, and proteins throughout the day)
  • Carbohydrate counting (for tracking the number of grams of carbohydrates consumed each day) is important for people with type 1 diabetes
  • Glycemic index (for tracking which carbohydrate foods increase blood sugar the most)


Tests for Glucose Levels

Both low blood sugar (hypoglycemia) and high blood sugar (hyperglycemia) are of concern for people who take insulin. It is important, therefore, to monitor blood glucose levels carefully as instructed by your provider. Depending on your type of diabetes and the medications you take you may be asked to measure your blood sugar from 0 to 7 times a day. In some cases, a continuous glucose monitor may be recommended.

In general, most adult people should aim for the following measurements goals (people with gestational diabetes may have different goals):

  • Premeal (preprandial) glucose levels of 80 to 130 mg/dL
  • Postmeal (postprandial) glucose levels of less than 180 mg/dL

Hemoglobin A1C Test 

Hemoglobin A1C (also called HbA1c or HA1c) is measured periodically up to every 3 months, or at least twice a year, to determine the average blood-sugar level over the lifespan of the red blood cell. While point of care (fingerstick) self-testing provides information on blood glucose for that moment, the A1C test shows how well blood sugar has been controlled over a period of several months. A1C goals should be individualized, but for most adults with well-controlled diabetes, A1C level goals should be less than 7%. For children, A1C should be less than 7.5%. (For people who do not have diabetes, normal A1C is <6%.) 

Other Tests 

Other tests are needed periodically to screen for potential complications of diabetes, such as high blood pressure, unhealthy cholesterol levels, and kidney problems. Such tests may also indicate whether current diet plans are helping the person and whether changes should be made. Periodic urine tests for albumin and blood tests for creatinine can indicate a future risk for serious kidney disease. 

Helpful Tips for Diet Maintenance 


Compared to fats and protein, carbohydrates have the greatest impact on blood sugar (glucose). There are three main types of carbohydrates: sugars, starches, and fiber. Dietary fiber is not digestible. Sugars and starches are eventually broken down by the body into glucose. 


Starches are broken down more slowly by the body than sugars. Some foods that are high in starch content are more likely to provide other nutritional components, as well as fiber: 

  • Vegetables, fruits, whole grains, beans, and dairy products are good sources of carbohydrates.
  • Whole grain foods such as brown rice, quinoa, bulgur, farro, oatmeal, and whole-wheat bread (when you can see the seeds and whole grains), provide more nutritional value than pasta, white rice, white bread, and white potatoes.


Fiber is an important component of many plant-based foods. There are two types of fiber: 

  • Soluble fiber attracts water and turns to gel during digestion. This slows digestion. Soluble fiber is found in oat bran, barley, nuts, seeds, beans, lentils, peas, and some fruits and vegetables. It is also found in psyllium, a common fiber supplement. Some types of soluble fiber may help lower cholesterol, but the effect on heart disease is not known.
  • Insoluble fiber is found in foods such as wheat bran, vegetables, and whole grains. It adds bulk to the stool and appears to help food pass more quickly through the intestines.


Sugars add calories, increase blood glucose levels quickly, and provide little or no other nutrients: 

  • Sucrose (table sugar) is the source of most dietary sugar, found in sugar cane, honey, and corn syrup.
  • Fructose, the sugar found in fruits, produces a smaller increase in blood sugar than sucrose. The modest amounts of fructose in fruit can be handled by the liver without significantly increasing blood sugar, but the large amounts in soda and other processed foods with high-fructose corn syrup overwhelm normal liver mechanisms and trigger production of unhealthy triglyceride fats.
  • A third sugar, lactose, is a naturally occurring sugar found in dairy products including yogurt and cheese.

People with diabetes should avoid products listing more than 5 grams of sugar per serving, and some providers recommend limiting fruit intake. Although moderation is important, fruits are an important part of any diet. They provide essential vitamins, minerals, and antioxidants, as well as fiber. You can limit your fructose intake by consuming fruits that are relatively lower in fructose (cantaloupe, grapefruit, strawberries, peaches, bananas) and avoiding added sugars such as those in sugar-sweetened beverages. Fructose is metabolized differently than other sugars and can significantly raise triglycerides, though usually a large intake of fructose is needed to do this (or drinking fructose sweetened beverages with a meal). 

In addition, limit processed foods with added sugars of any kind. Pay attention to ingredients in food labels that indicate the presence of added sugars. These include terms such as sweeteners, syrups, fruit juice concentrates, molasses, and sugar molecules ending in “ose” (like dextrose and sucrose). 

Artificial sweeteners use chemicals that mimic the sweetness of sugar. They include aspartame (NutraSweet, Equal), sucralose (Splenda), saccharin (Sweet’N Low), and rebiana (Truvia). (Rebiana is an extract derived from the plant stevia.) These products do not contain calories and do not affect blood sugar. Artificial sweeteners can help with weight control, but it is important not to consume extra calories elsewhere. Artificial sweeteners have become more controversial in the past few years. Consumption of some artificial sweeteners is even associated with weight gain. 

The Carbohydrate Counting System 

Some people plan their carbohydrate intake using a system called carbohydrate counting. It is based on these premises: 

  • All carbohydrates (either from sugars or starches) will raise blood sugar to a similar degree based on the weight, although the rate at which blood sugar rises depends on the type of carbohydrate and on the individual. A higher peak won’t last as long while a lower peak may take longer to return to premeal blood sugar levels, but the total area under the curve for the increase in blood sugar will be similar.
  • Carbohydrates have the greatest impact on blood sugar. Fats and protein play only minor roles.
  • Carbohydrate counting is very important for people with type 1 diabetes and anyone on an insulin regimen. Carbohydrate counting can even help control blood glucose levels in people with type 2 diabetes who are not on insulin regimens.

The basic goal of carbohydrate counting is to balance insulin with the amount of carbohydrates eaten in order to control blood sugar (glucose) levels after a meal. There are several options for counting carbohydrates. It’s best to work with an RD. 

A dietitian can create a meal plan that accommodates the person’s weight and needs. Many people with type 1 diabetes work with their providers to determine a carbohydrate to insulin ratio. This special calculation tells the person how much insulin they need to take to cover a certain amount of carbohydrate in the meal. A common ratio would be 1 unit of insulin for 15 grams of carbohydrate. Then if you choose a meal with 60 grams of carbohydrate you know you need 4 units of insulin to match the carbohydrates and prevent the meal from increasing your blood sugar level. When people learn how to count carbohydrates and adjust insulin doses to their meals, many find this system more flexible, more accurate in predicting blood sugar increases, and easier to plan meals than other systems. 

The Glycemic Index 

The glycemic index helps determine which carbohydrate-containing foods raise blood glucose levels more or less quickly after a meal. The index uses a set of numbers for specific foods that reflect greatest to least delay in producing an increase in blood sugar after a meal. The lower the index number, the better the impact on glucose levels. This system is artificial in that the number is calculated when eating only that food. The index for mashed potato is 72, but eating the same amount of mashed potato with gravy, green beans and grilled chicken breast would change the absorption time significantly. The index also does not account for variation in food preparation. The lower (good) glycemic index of brown rice can be increased (bad) just by increasing the cooking time. The index also does not account for mixed meals. For example, eating white rice with a sauce that includes chicken, vegetables and coconut milk will change the glycemic index vs. eating white rice alone. 

There are two indices in use. One uses a scale of 1 to 100 with 100 representing a glucose tablet, which has the most rapid effect on blood sugar. [See Table: “The Glycemic Index of Some Foods,” below.] The other common index uses a scale with 100 representing white bread (so some foods will be above 100). 

Choosing foods with low glycemic index scores may have a modest effect on controlling the surge in blood sugar after meals. Substituting low- for high-glycemic index foods may also help with weight control. 

One easy way to improve glycemic index is to simply replace starches and sugars with whole grains and legumes (dried peas, beans, and lentils). However, there are many factors that affect the glycemic index of foods, and maintaining a diet with low glycemic load is not straightforward. 

No one should use the glycemic index as a complete dietary guide, since it does not provide nutritional guidelines for all foods. It is simply an indication of how the body will respond to certain carbohydrates.

Weight Control for Type 2 Diabetes 

The American Diabetes Association recommends that overweight and obese people aim for a small but consistent weight loss of ½ to 1 pound (0.2 to 0.5 kilogram) per week. For overweight and obese people with diabetes, high intensity short-term programs of dieting, physical exercise, and behavioral interventions are recommended initially for achieving at least 5% weight loss over 3 to 6 months. If this goal is achieved, long-term programs are then recommended for weight maintenance. A registered dietician can compute a daily calorie goal for you based on your height, weight, age, sex, and activity level. Some registered dieticians are also certified diabetes educators. 

Even modest weight loss can reduce the risk of heart disease and diabetes. According to the American Diabetes Association (ADA), low-carbohydrate, low-fat calorie-restricted, or Mediterranean diets may help reduce weight in the short term (up to 2 years). Physical activity and behavior modification are also important for achieving and maintaining weight loss. 

Here are some general weight loss suggestions that may be helpful: 

  • Start with realistic goals. When overweight people achieve even modest weight loss they reduce risk factors in the heart. Ideally, overweight people should strive for 7% weight loss or better, particularly people with type 2 diabetes.
  • A regular exercise program (at least 150 minutes of moderate exercise per week) is essential for maintaining weight loss. Recommended goals are 90 minutes/day for weight loss, 60 minutes/day for maintenance, and 30 minutes/day for overall heart health and prevention of weight gain. The 150 minutes per week should be spread over at least 3 days and you should have no more than 2 consecutive days without exercising. Check with your provider before starting any exercise program.
  • For people who cannot lose weight with diet alone, weight-loss medications may be considered.
  • For severely obese people (a body mass index >40, or >35 with comorbidities), weight loss through bariatric surgery can help produce rapid weight loss, and improve insulin signaling and glucose levels in people with diabetes.