While Type 1 and Type 2 diabetes are widely recognized and studied, scientists have proposed two additional forms - type 3 and type 4 diabetes. Though they are not medically or officially classified by any health organizations, these terms have been gaining attention more and more.Recently, Health and Me reported on the Type 5 diabetes, which is linked to malnutrition. However, the question is, if we already have type 1, 2, and 5 diabetes, then what are the type 3 and 4?Let's delve a little deeper into that:What is Type 3 Diabetes?Type 3 Diabetes is an unofficial term that is used to describe Alzheimer's disease which is caused by insulin resistance in the brain. Researchers first proposed this classification after observing similarities between the brain changes in Alzheimer's and those caused by diabetes.In healthy brains, insulin usually supports communication between the nerve cells and also helps regulate energy use. However, in people with Alzheimer's, the brain shows signs of insulin resistance, impairing the brain's ability to use glucose properly. This dysfunction can also lead to memory loss, cognitive decline, and the buildup of proteins like tau and beta-amyloid, hallmarks of Alzheimer's disease.While Type 3 diabetes is not a formally recognized diagnosis, the idea does throw a light on its important link between metabolic health and brain function.What are the symptoms?Memory loss that disrupts daily lifeDifficulty solving problems or planningTrouble completing familiar tasksConfusion with time or placeProblems with language and communicationLosing items or placing them in odd locationsPoor judgment or decision-makingWithdrawal from work or social activitiesMood swings and personality changesWhile some of these changes can occur with age, consistent or worsening symptoms should prompt a medical evaluation.What Causes It?The idea of type 3 diabetes is based on how insulin dysfunction in the brain may contribute to neurodegeneration. Several risk factors have been identified:Diet high in sugar and fat, low in fiberSedentary lifestyleChronic stressLow socioeconomic statusGenetics, including the presence of the APOE4 geneHigh blood pressure and poor lipid metabolismThese factors can impair glucose delivery to the brain and damage neurons, increasing the risk of dementia.What is Type 4 Diabetes?It is also another proposed category that occurs in older adults who develop insulin resistance despite not being overweight. In fact, in a 2015 study that involved mice, suggested that this form of diabetes may be caused by accumulation of immune cells called regulatory T cells, which increase with age. The study is titled: Depletion of Fat Tregs Prevents Age-Associated Insulin Resistance.Unlike type 2 diabetes, which is also linked to obesity, in type 4 diabetes, lean individuals get affected.Symptoms of Type 4 DiabetesFatigueFrequent urinationBlurred visionUnexplained weight lossIncreased thirst and hungerSlow-healing soresBecause it typically affects older adults with normal body weight, these symptoms may be misattributed to aging or other conditions, leading to underdiagnosis.What Causes It?The exact causes of type 4 diabetes are still being studied, but aging appears to play a significant role. Research indicates that excess regulatory T cells may interfere with insulin signaling, leading to blood sugar issues in the absence of typical risk factors like obesity.