Type 2 diabetes develops when a person has insulin resistance. Insulin resistance means that the body is no longer sensitive to insulin and cannot use it correctly. In time, the body may stop producing this hormone.

When insulin resistance starts, there are no signs and symptoms of diabetes, and blood sugar levels are normal.

Excess weight appears to increase the risk of developing insulin resistance and diabetes. Therefore, losing weight may help a person prevent these conditions.

According to the Centers for Disease Control and Prevention (CDC), in 2015, more than 84 million people in the United States had prediabetes, while more than 30 million had diabetes. The majority of the latter group had type 2 diabetes, which results from insulin resistance.

In this article, we look at the link between insulin resistance and excess weight. We also explain how losing weight might prevent or reverse insulin resistance.

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Losing weight may help a person improve their sensitivity to insulin.

To appreciate the function of insulin, we need to understand how the body takes in and uses energy. The body's cells need energy for all of their functions, from running to thinking and breathing. Without energy, a person's cells will die, and this will be fatal.

When a person eats, the body absorbs nutrients from the food, including carbohydrates. During digestion, it converts carbs into blood glucose, or sugar, and this enters the body's cells to provide them with energy.

Insulin is a hormone that comes from the pancreas. It enables the blood sugar to move out of the blood and into the body's cells.

The development of insulin resistance marks the beginning of diabetes. When a person has insulin resistance, their body cells stop responding to insulin in the usual way. This loss in sensitivity to insulin means that they begin to lose the ability to take in glucose.

In response, the pancreas boosts its insulin production so that glucose can continue to enter the cells. At first, this will help. The cells will have energy, and blood sugar levels will not rise.

However, as the cells' resistance to insulin increases, the pancreas needs to produce more and more insulin. Eventually, it becomes unable to create enough insulin to move the glucose out of the blood and into the cells.

At this point, blood sugar reaches levels that are high enough for a doctor to diagnose prediabetes.

Fasting blood sugar levels are as follows:

  • Normal: Under 100 milligrams per deciliter (mg/dl)
  • Prediabetes: 100–125 mg/dl
  • Diabetes: 126 mg/dl and above

A doctor can test a person's fasting blood glucose level, or an individual can check their glucose levels at home.

Blood glucose testing kits for home use are available for purchase online.

Initially, insulin resistance does not cause any symptoms, but health problems will appear in time unless a person takes action. As there are no symptoms, any action at this time must be preventive.

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A person may find out that they have insulin resistance during routine screening.

A person who has risk factors for diabetes may have insulin resistance without knowing it. Even if their blood sugar levels are normal, they should take steps to prevent diabetes.

Scientists do not know exactly what causes insulin resistance, but the following factors appear to play a role:

  • excess weight or obesity
  • extra fat around the abdomen, even with a healthy body mass index (BMI)
  • low levels of physical activity
  • a diet that is high in unprocessed carbs, such as sugar and white flour

Taking action in the early stages can prevent or reverse prediabetes. If a person does not take action, the body will not be able to produce enough insulin, and there will be too much glucose in the blood.

In time, as this glucose travels around the body, it can damage the blood vessels, nerves, and body organs, leading to severe and life-threatening complications.

Research has found that a weight loss of 5–7 percent is enough to reduce the risk of diabetes by 58 percent in a person who has a high risk of the condition. For someone who weighs 200 pounds (lb), this would be a loss of 10–14 lb.

For a person with diabetes or a high risk of diabetes, losing weight and maintaining a healthy weight can help reduce the risk of insulin resistance, prediabetes, diabetes, and the health complications that can result.

People with insulin resistance, prediabetes, or a high risk of diabetes need a long-term dietary and lifestyle strategy to protect their health. A "crash diet" will not reduce insulin resistance.

The CDC's National Diabetes Prevention Program emphasizes eating more healthful foods and doing at least 150 minutes of physical activity each week.

These strategies can help a person lose weight and build healthful habits for life.

Choosing healthful foods that include plenty of fresh fruits and vegetables, being mindful of portion sizes, and moderating carbohydrate intake are three of the most important factors in a sustainable, healthful diet.

The DASH eating plan, which the National Institutes of Health (NIH) developed, is a healthful, long-term diet. DASH stands for Dietary Approaches to Stop Hypertension.

The diet does not focus on calorie control but instead encourages people to eat:

  • plenty of fruit and vegetables
  • low-fat dairy products
  • nuts and seeds
  • beans and pulses

It advises people to avoid empty carbohydrates and sugars and to increase their intake of nutrient-rich foods and heart-healthy proteins.

The DASH diet is more suitable for long-term application than a crash diet or many calorie-controlled diets. This dietary approach also provides high fiber intake, which helps manage blood sugar levels by slowing the absorption of carbohydrates and reducing the need for insulin.

Click here to learn more about how diet can help with insulin resistance.

Weight loss and a healthful diet are important ways of reducing the chance of developing insulin resistance, but adding other strategies will lower the risk further.

Quitting smoking

Some studies have suggested that regular use of tobacco products may increase the risk of diabetes and insulin resistance. Others, however, have not found evidence of a direct link.

A 2016 study looking at the data of nearly 6,000 people concluded that there may not be a direct link between smoking and insulin resistance but that it may still play a role in causing diabetes in combination with other factors.

However, smoking is a risk factor for heart disease, lung infections, and other health conditions that are also complications of diabetes. Smoking can worsen these issues too.

For this reason, a person with insulin resistance or a high risk of diabetes should quit smoking if necessary and avoid secondhand smoke where possible. A doctor can help a person find resources and strategies to make quitting easier.

Physical activity

Regular activity can improve insulin resistance because the muscles use up glucose from the bloodstream and do not require insulin.

The Physical Activity Guidelines for Americans recommend that adults do a minimum of 150 minutes of moderate-intensity aerobic exercise or 75 minutes of vigorous-intensity aerobic exercise each week.

For the best results, people should combine cardiovascular training with muscle-building exercises and stretching.

It is best to talk to a doctor before beginning a new exercise plan, especially if a person has not been physically active for some time.

Vitamin D

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A vitamin D deficiency is common with type 2 diabetes.

Some research has found that people with diabetes are more likely to have low vitamin D levels.

However, there is not yet any evidence that taking vitamin D supplements can prevent diabetes or prediabetes. In one study, researchers have found that taking vitamin D supplements did not affect blood sugar levels in people with well-managed diabetes.

The Office of Dietary Supplements recommend that people aged 1–70 years should consume 600 international units (IU) of vitamin D a day from dietary sources.

While sunlight is by far the most concentrated source of vitamin D, dietary sources include:

  • oily fish
  • fortified milk and other dairy products
  • fortified cereal
  • egg yolks

People should ask their doctor about whether vitamin D supplementation is appropriate for them.

Learn more here about vitamin D and its sources.

Sleep

Insufficient or poor-quality sleep can increase a person's risk of developing insulin resistance and type 2 diabetes.

The authors of a 2015 study noted that for people with diabetes, sleep is "an additional lifestyle behavior, important for metabolic health and energy homeostasis."

Getting plenty of sleep each day can help regulate the hormones that play a role in hunger and reduce the risk of glucose metabolism dysfunction.

Medication

Some people need medication to help improve insulin sensitivity, especially when dietary and lifestyle changes have not been effective. Doctors often prescribe metformin or other medicines for this purpose.

Learn more here about the medications available for managing diabetes.

A diagnosis of insulin resistance does not automatically mean that a person has diabetes, but, without intervention, diabetes can develop.

Achieving and maintaining a suitable target weight can reduce the risk of developing type 2 diabetes.

People with insulin resistance, prediabetes, or diabetes should ask their doctor about a suitable weight-loss plan.

Healthful eating habits are crucial for losing weight, maintaining a healthy weight, and preventing insulin resistance.