TOFI   (thin-outside-fat-inside) is used to describe lean individuals with a disproportionate amount of fat (adipose tissue) stored in their abdomen. The figure to illustrate this shows two men, both 35 years old, with a BMI of 25 kg/m². Despite their similar size, the TOFI had 5.86 litres of internal fat, whilst the healthy control had only 1.65 litres.

Subjects defined as TOFI with body mass index (BMI) 25 kg/m² have increased levels of many of the risk factors associated with the metabolic syndrome. This phenotype is a further refinement of "metabolically-obese normal-weight" (MONW).

Subjects defined as TOFI have been described as being at higher risk of developing insulin resistance and type II diabetes due to the fact that they have reduced physical activity/VO₂max, reduced insulin sensitivity, higher abdominal adiposity, and a more atherogenic lipid profile. Another important characteristic observed in this cohort is elevated levels of liver fat. It is shown that overconsumption of fructose can lead to TOFI by inducing inflammation associated cortisol release.

Visceral fat, the kind found deep inside your abdomen, is especially dangerous because it secretes inflammatory chemicals directly ​into your liver. As fat accumulates inside of your abdomen, it ​starts to crowd your internal organs and muscles, particularly the ​diaphragm. It can restrict blood supply to your vital organs, and ​it also makes it hard for your diaphragm to do its work.

How You Breathe

​Your diaphragm is a dome-shaped sheet of muscle that ​separates your chest from your abdominal cavity. When you inhale, your diaphragm contracts (tightens) and moves downward, creating a vacuum in your lungs and causing air to rush into them. The downward contraction of your diaphragm increases the space in your chest cavity, allowing your lungs to expand. The intercostal muscles between your ribs also help to enlarge the space in your chest. These muscles contract as ​you inhale, pulling your rib cage both upward and outward.

Visceral fat is found deep inside your ​abdomen, surrounding your vital ​organs. It’s dangerous because it ​secretes toxic chemicals that travel​ directly into your liver and then into your bloodstream, causing many metabolic and cardiovascular disorders.

Subcutaneous fat is the kind that lies just under your skin. You can pinch it ​between your fingers. Most people don't like having too much of it, but ​it’s not as dangerous to your health ​as visceral fat.

Why is physical activity important?

Regular physical activity provides immediate and long-term health benefits. Being physically active can improve your brain health, reduce the risk of disease, strengthen bones and muscles, and improve your ability to do everyday activities.

Physical activity also helps:

• Improve sleep quality.
• Reduce high blood pressure.
• Reduce risk for type 2 diabetes, heart attack, stroke, and several forms of cancer.
• Reduce arthritis pain and associated disability.
• Reduce risk for osteoporosis and falls.
• Reduce symptoms of depression and anxiety.

In addition, physical activity is important if you are trying to lose weight or maintain a healthy weight.

• When losing weight, more physical activity increases the number of calories your body uses for energy. Using calories through physical activity, combined with reducing the calories you eat, creates a calorie deficit that results in weight loss.
• Most weight loss occurs from decreasing caloric intake. However, evidence shows the only way to maintain weight loss is to be engaged in regular physical activity.
• Most importantly, physical activity reduces risks of cardiovascular disease and diabetes beyond that produced by weight reduction alone.

How much physical activity do I need?

To maintain your weight: Work your way up to 150 minutes of moderate-intensity aerobic activity each week. This could be brisk walking 30 minutes a day, 5 days a week. Or you could do 75 minutes of vigorous-intensity aerobic activity each week, such as swimming laps.

The exact amount of physical activity needed to maintain a healthy weight varies greatly from person to person. You may need more than the equivalent of 150 minutes of moderate-intensity activity a week to maintain your weight.

To lose weight and keep it off: You will need a high amount of physical activity unless you also adjust your diet to reduce the number of calories you eat and drink. Getting to and staying at a healthy weight requires both regular physical activity and a healthy eating plan.

What do moderate- and vigorous-intensity mean?

Moderate: While performing the physical activity, if your breathing and heart rate is noticeably faster but you can still carry on a conversation — it’s probably moderately intense. Examples include:

• Walking briskly (a 15-minute mile).
• Light yard work (raking/bagging leaves or using a lawn mower).
• Light snow shoveling.
• Actively playing with children.
• Biking at a casual pace.

Vigorous: If your heart rate is increased substantially and you are breathing too hard and fast to have a conversation, it’s probably vigorously intense. Examples include:

• Jogging/running.
• Swimming laps.
• Rollerblading/inline skating at a brisk pace.
• Cross-country skiing.
• Most competitive sports (football, basketball, or soccer).
• Jumping rope.

How many calories are used in typical activities?

The following table shows calories used in common physical activities at both moderate and vigorous levels.

Think of the typical person with type 2 diabetes. Did you imagine someone older, overweight, inactive? You’d be partly right, but the big picture is more complicated and far-reaching.

Age

People are developing type 2 diabetes younger than ever. Also, the disease progresses faster in younger people than older ones. Complications related to diabetes such blindness and kidney disease are increasingly a young person’s problem.

Weight

Being overweight is a major risk factor for developing type 2 diabetes. But the inch you can pinch (subcutaneous) isn’t the most troubling kind of fat. Hidden layers of fat around organs (visceral) are thought to drive up the risk for heart disease, diabetes, and stroke. Normal-weight people who are TOFI—thin outside, fat inside—may look healthy but still have excess visceral fat that increases their risk.

Activity

Older folks aren’t the only ones not moving enough—fewer than 3 out of 10 high school students get the recommended 60 minutes or more of physical activity every day. Getting less than 150 minutes of physical activity a week is a risk factor for diabetes. Increasing physical activity, on the other hand, is especially effective at reducing the visceral fat mentioned above.