Why is fat bad for you: how body fat works

Why is fat bad for you: how body fat works

The most pressing questions about body fat, skinny fat and visceral fat answered in plain English.

Fat has been the most reviled component of the body for several decades now. So we've decided it's time to explain why fat is, like most things, good and bad at the same time.

This is what happens when Atlas Biomed doctors and researchers take their heads out of science journals and try to apply their smarts to everyday questions, like body fat.

  • 1. What is fat?
  • 2. What is fat used for in the body?
  • 3. What is visceral fat?
  • 4. What diseases are linked to visceral fat?
  • 5. What is skinny fat?
  • 6. How to lose belly fat?
  • 7. Which fats are bad for cholesterol?
We hope you enjoy the second part of our series about good fats and bad fats. We initially wrote one big article that covered body and dietary fats. Then we decided that, like a well-balanced meal, portion control was required.

What is fat?

Excellent question. First off, it’s important to distinguish dietary fat and fat in the body. The most common misconception is that, somehow, fats in food that you eat, enter the body and magically remain in that state, migrating directly to deposit themselves on your hips, belly and in your arteries. But that's not quite accurate. If it were, we’d all taste delicious, right!?!

Technically speaking, fat is an organic compound with solvent properties that doesn’t dissolve in water. Your body needs fat, also called lipids because fat is a vital metabolic and structural compound.

Bread toasts with avocado, banana, tomato. Easy to make, great for a quick breakfast.
Photo by Ella Olsson / Unsplash

Fat can enter the body through food, where it is broken down by pancreatic enzymes and bile salts in the stomach and small intestine. From there, it eventually makes it to the bloodstream with a little help from the lymphatic system.

When insulin levels are high, the body stores more fat. Insulin is a hormone the body uses to manage glucose levels in the blood. Nowadays many people are overweight due to the high levels of sugar in their diet.

Sugar is also turned into fat by the body, a process that is stimulated by high levels of insulin. This is called insulin resistance and it is a precursor for diabetes type II. According to Diabetes UK, one in ten British adults over 40 now have this chronic disease.

The body has limited subcutaneous fat stores in the skin. When they run out, fat accumulates around the organs. This is called visceral fat and it can have serious health risks for humans.

Fats and complex sugars in whole carbohydrates like avocados are tied up in a web of nutrients including dietary fibre. Dietary fibre has the ability to lower the energy extracted from food by making it harder to pass through the bowel wall.

In short, fibre reduces the calories absorbed from whole foods by the body, supports a healthy gut microbial ecosystem and encourages frequent and healthy bowel movements.

☝️READ MORE☝️ Find out more on this topic in the question: What is visceral fat?

What is fat used for in the body?

As we've established, fats don't just enter the body and set up shop on your thighs or belly. Remember, your body is a formidable computer that knows what it needs. Here's what your body uses fat for:

cell membranes signalling molecules
nerve cells sex hormone synthesis
vitamin synthesis thermoregulation
energy storage protects vital organs

And we think you'll agree, these are pretty vital tasks. So don't fear fat, just steer clear of trans fats and consume saturated fat in moderation. You can learn all about good and bad dietary fats in last week's Ultimate guide to good fats and bad fats in food.

What is visceral fat?

Visceral fat is body fat that envelopes your organs, especially those in the abdomen, like the intestines, kidneys and liver. Basically, it pads the space between the organs.

Visceral fat is also known as metabolically active fat because it plays a role in inflammation. High levels of visceral fat are associated with several chronic and deadly diseases.

What diseases are linked to visceral fat?

diabetes type II heart disease
breast cancer bowel cancer
Alzheimer’s obesity
Research now indicates that the ratio of visceral to subcutaneous fat is a biomarker for Crohn’s disease, a member of the inflammatory bowel disease family.

What is skinny fat?

Skinny fat is a colloquial term that refers to people who look slim so they appear to be healthy because they are not overweight. However, they are carrying too much visceral fat and don't have enough lean muscle.

Being skinny fat is taken seriously by medical professionals, who call it sarcopenic obesity. That's right, O-B-E-S-I-T-Y. And it is linked to the same disease risks as obesity, like cardiovascular disease and diabetes type II.

That's because excess visceral fat can activate the immune system, causing inflammation, and that's why it's associated with several preventable and chronic diseases.

How does one become skinny fat? The most prominent risks include a sedentary lifestyle, poor diet and lack of exercise. However, remember that sarcopenic obesity, although a relatively novel addition to the doctor's handbook, is not measured by eyeballing a patient and declaring them skinny fat - there are diagnostic tools.

☝️READ MORE☝️ Find out more on this topic in the question: What is visceral fat?

How to lose belly fat?

Nowadays, it's not unusual to want a flat stomach, a few ribs on display and a six-pack. Or just to get rid of the muffin top. And that’s okay because secretly most of us do. Who wouldn’t in a world where we are bombarded with pictures of underweight people in swimsuits with 8-pack abs?

There’s no easy way to lose belly fat, and don’t believe any service, pill or website that tells you otherwise. No amount of ab crunches alone will turn you into Chris Hemsworth or the lovechild of a pirate and an angel.

Hikers on W trek
Photo by Toomas Tartes / Unsplash

Fortunately, your body has been designed by evolution for movement, to eat whole foods and to be outside. These are the basic pillars of our existence and an excellent place to start.

If you're just starting out on your journey to health, aim to get your 5 fruit and veg per day as a baseline, cut down on meat, processed foods and alcohol. Make your own meals and adopt a routine.

When it comes to exercise, don't punish yourself. Set small achievable goals in your daily routine to move and use calendar reminders to stay on track. And remember, WALKING COUNTS!

The NHS has laid out some basic guidelines for weekly exercise to get the health benefits, it's a great place to start.

OPTION 1 150 minutes of moderate aerobic activity like cycling/walking
2 strength workouts for all major muscle groups
OPTION 2 75 minutes of vigorous aerobic activity like running
2 strength workouts for all major muscle groups
OPTION 3 A mix of moderate and vigorous aerobic activity
2 strength workouts for all major muscle groups


Which fats are bad for cholesterol?

Trans fats, also known as partially hydrogenated oils, occur in processed foods and deep-fried foods. They are known to lower “good” HDL cholesterol and increase “bad” LDL cholesterol.

Research has linked trans fats to many diseases including colon cancer, diabetes and heart disease. You can learn all about trans fats and saturated fat in last week's article, the ultimate guide to good fats and bad fats in food.

Leigh Stewart
Leigh Stewart Head of Atlas Biomed content, trained chef and avid fermenter of edible bacteria.

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