I know what many of you are thinking. Oh no! Not another post on “good fats” and “bad fats”, how saturated fat is NOT KILLING you! No, this post is not about dietary fat. I am talking about your body’s natural fat and how your body’s fat distribution decides your health.
Body fat or adipose tissue is not just a mass of fatty material lying around as inert weight. Without going into much details I will summarise a few important features.
- There are different types of adipocytes that are broadly classified into white, brown, or beige adipocytes.
- White adipocytes help store energy,
- Brown adipocytes help in generating body heat (thermogenesis)
- The function and origin of beige cells is less clear and is under investigation.
- Adipocytes are recognized as critical regulators of whole-body metabolism.The major ones being lipid metabolism, blood sugar control, regulation of blood pressure, blood clotting and inflammation.
- Insulin resistance. (More on insulin resistance in other post/video)
- Fat cells secrete hormones that regulate energy homeostasis in other tissues. Leptin, Adiponectin and Resistin are the important ones.
- Adipocytes secrete inflammatory substances called adipokines. There are about 50 known ones that are secreted by fat cells.
- Adipocytes are involved in sex hormone metabolism through the enzyme aromatase. (This is very important in deciding you risk for breast and prostate cancers).
- Hormone disrupting chemicals (EDC) ,environmental toxins are stored in fat (and they also increase fat store).
WHERE IS THIS FAT (ADIPOSE TISSUE) LOCATED?
Although the amount of total body fat is strongly associated with insulin resistance,heart disease, stroke, diabetes, cancer and dementia,it is becoming increasingly clear that different fat compartments contribute differentially to these risks.
From:Fuster, José J., et al. "Obesity-induced changes in adipose tissue microenvironment and their impact on cardiovascular disease." Circulation research 118.11 (2016): 1786-1807.
Brown Adipose Tissue: This is present mostly around the neck and its main function is in generating body heat. Newborn babies have more of this fat. It is also called the “good fat”.
Perivascular Adipose Tissue: This is the fat present around blood vessels. It was long thought to have only a supporting role, but is now understood to have a major role in health and disease. It secretes biologically active chemicals and is involved with blood vessel inflammation.
Bone Marrow Adipose Tissue: As the name implies, this is the fat in bone marrows. Not a lot is known about its function yet, but it is probably related to bone mass.
Ectopic Hepatic Lipids: This is the fatty liver (Non-Alcoholic fatty Liver Disease NAFLD) that develops due to consumption of excess carbohydrates-“diabetes of the liver”. It is related to insulin resistance and is a risk factor for diabetes, heart disease and many more diseases. Fatty liver (NAFLD) can progress to NASH (Non-Alcoholic Steatohepatitis), fibrosis, cirrhosis and liver cancer. NAFLD is like an epidemic worldwide.
Subcutaneous Adipose Tissue (SAT) and Visceral Adipose Tissue (VAT): The acronym VAT reminds me of Hindi movies of the seventies where the villain usually drank VAT 69 , the whisky ! Excess VAT, ie the body’s VAT ,is fat that accumulates among the internal organs. This is very distinct from the SAT , which is fat beneath the skin. Excess VAT is related to a whole host of cardiometabolic diseases. Increased belly fat is usually excess VAT. SAT probably has protective functions. The apple-shaped body versus the pear-shaped body!
Epicardial Adipose Tissue: This is the fat present between 2 layers of the heart. I will not discuss all the different types of cardiac fat here, except to mention that excess epicardial fat is associated with many diseases like coronary artery disease (CAD),which is atherosclerotic thickening of the blood vessels supplying the heart, and insulin resistance.
Amongst all the different types of adipose tissue the ones most relevant to health (as far as knowledge goes today) are brown fat,SAT, VAT, liver fat and fat in the heart.
HOW DO YOU KNOW IF YOU HAVE EXCESS FAT IN THESE COMPARTMENTS?
Waist measurement and Waist-Hip Ratio:
As many of you know your BMI is not the best measure of health. This is particularly so for South Asians.This is because many of you are TOFI–Thin-Outside-Fat-Inside or “Skinny Fat”. This means that at a given body weight , you may have a higher body fat percentage than is healthy for you.
KNOW YOUR NUMBERS:
Men: Waist circumference 85-90 cm (34”) or more is unhealthy.
Women: Waist circumference 80 cm (31.5”) or more is unhealthy.
The easiest way to measure this is by measuring your waist size with a tape measure at the level of the belly button.
Waist to Hip Ratio:
Divide your waist circumference by your hip circumference.
Hip circumference: Measure the circumference of your hips at the widest point of your buttocks.
Healthy Waist/Hip ratio : Men 0.90 , Women 0.80.
Blood Tests: (Basic)
- Fasting Blood Sugar
- Post Meal Blood sugar
- Fasting Insulin.
- AST,ALT (SGOT,SGPT)
Weighing Scales :
Weighing scales that show your body fat and lean mass percentage are acceptable measures of health.
Ultrasonography of whole abdomen can detect fatty liver.
Echocardiography: To detect heart function and fat.Currently, there is no consensus on the ‘gold standard’ for quantification of cardiac fat.
MRI: Costs more.
PET, DXA,CT scans: Radiation exposure. I don’t usually recommend these tests only to quantify body fat.
- If you have belly fat, it puts you at a high risk for diseases like diabetes, heart disease, dementia, cancer.
- Belly fat relates to insulin resistance.
- You do not get fat by eating good quality fat. It is very likely that you eat more carbohydrate than is good for you.
- A recent study called the PURE study in a prestigious journal The Lancet,showed that eating excess carbohydrate , not saturated fat puts you at higher risk of dying.
- Dietary carbohydrate gets stored as body fat.
- Know your basic blood numbers. (You will need someone knowledgeable in this field to interpret the numbers. Please remember that “in normal range” is not necessarily optimal).
- If you are insulin resistant it is very likely that you have fatty liver and higher cardiac fat.
- Total body weight is not the best measure of health.—Remember TOFI! This means that your skinny friend may not necessarily be healthy!
Porter, Stacy A., et al. "Abdominal subcutaneous adipose tissue: a protective fat depot?." Diabetes care 32.6 (2009): 1068-1075. Dehghan, Mahshid, et al. "Associations of fats and carbohydrate intake with cardiovascular disease and mortality in 18 countries from five continents (PURE): a prospective cohort study." The Lancet (2017).