Insulin and Insulin Resistance: The Ultimate Guide

Normally, insulin is produced in small amounts throughout the day (basal amount) and in large amounts after meals (bolus phenomenon):

• The basal amount is required to metabolize glucose and glycogen and prevent muscle breakdown.
• The bolus amount controls the entry of blood sugar (after meals) into the liver and muscle cells. It controls satiety via an indirect action on the hunger hormones adiponectin, leptin, and ghrelin.

In the absence of insulin (type I diabetes) or in the presence of insulin resistance (type II diabetes), the insulin-cell interaction is disrupted. Insulin can no longer act on the cell membranes (due to unavailability or lack of response), which has a negative effect on energy metabolism.

The available glucose stays in the blood, binds with the proteins in the lining of blood vessels (glycation) and organs, and initiates a pro-inflammatory state in the body. This causes damage to cells in various organs.

Insulin resistance is a condition in which the body's capacity to react to the effects of insulin is decreased, particularly in the case of muscle and adipose (fat) tissues. Insulin resistance causes muscle breakdown as the body starts to utilize protein instead of carbs for energy.

The more sugar (i.e., carbs) you consume, the higher your insulin levels. As your insulin levels rise, the less fat you burn and the more sugar you store in your fat cells. This also causes weight gain, which in turn can increase insulin resistance. Insulin prevents fat from being broken down and retains that fat locked up in your fat cells, preventing your body from burning it.

Over time, insulin resistance can lead to excessive blood sugar levels and eventually, prediabetes and type II diabetes. 

According to estimates, 25% of Americans suffer from insulin resistance.

Insulin resistance typically causes no symptoms unless it progresses to diabetes. According to the CDC, 90% of people with insulin resistance are unaware of their condition. Signs may include:

• Abdominal obesity
• Elevated blood sugar levels
• Dark skin patches
• Skin tags
• Large pores and acne
• Thickened skin
• Polycystic ovarian syndrome
• Irregular menstrual cycle
• Hair loss
• Swollen ankles
• Carb cravings
• Lethargy or tiredness
• Excessive hunger
• Difficulty concentrating
• High blood pressure
• High cholesterol levels
• Features consistent with endocrine conditions, such as acromegaly and Cushing syndrome

Insulin resistance can be detected with a glucose tolerance test to measure glucose levels or by measuring fasting insulin levels in the morning. An accurate diagnosis can be made based on the specific characteristics of the patient even when insulin resistance has not been tested.

The cause of insulin resistance is unknown. However, studies show that a combination of the following factors may lead to insulin resistance:

• Family history of insulin resistance
• Genetics (South Asian population)
• Advancing age
• Obesity
• Sedentary lifestyle
• Pregnancy
• Certain medications such as glucocorticoids
• Chronic stress
• Smoking
• Cushing syndrome
• Polycystic ovary disease
• Sleep disorders 
• High blood pressure
• High cholesterol levels
• Poor diet (high in fat, salt, and sugar)

Insulin resistance can lead to metabolic syndrome or syndrome X, which occurs when the following conditions are present:

• Elevated blood pressure
• High blood glucose levels (blood sugar)
• Abnormal cholesterol or triglyceride levels
• Excessive abdominal fat (waist size greater than 35 inches in women or 40 inches in men)

Metabolic syndrome considerably raises the risk of cardiovascular disease, stroke, and diabetes.

Insulin resistance is often associated with prediabetes and diabetes because of the diminished ability of the pancreas to generate insulin over time. When this happens, the body is no longer able to control blood sugar levels without medication.

• Prediabetes: Blood sugar levels of 100-124
• Diabetes: Blood sugar levels over 125

Diabetes carries serious health risks, including:

• Kidney disease
• Increased risk of heart attack and stroke
• Nerve damage
• Impaired circulation
• Weakened immune system
• Death

Chronically raised insulin levels stimulate cell and tissue development. This contributes to further weight gain and increases the risk of cancer. If you have diabetes, you may be prescribed metformin, which helps regulate the release of glucose from the liver into the blood and makes cells more sensitive to insulin.

Dietary and lifestyle changes can help you manage or prevent insulin resistance. To lower insulin levels in the body, the following are some suggestions that may help:

• Stay physically active
• Exercise 30 minutes a day at least 4 times a week
• Eat more fiber
• Include fatty fish in your diet at least twice a week
• Cut down on refined carbs
• Avoid or limit sugar intake
• Watch protein intake
• Monitor overall calorie intake
• Try fasting once a week
• Talk to a dietitian about herbs and supplements that can help lower your insulin levels