Читать книгу The GI Walking Diet: Lose 10lbs and Look 10 Years Younger in 6 Weeks - Joanna Hall - Страница 34

Most body fat is stored in fat cells called adipocytes. Around 50,000–60,000 calories of energy are stored as triglycerides in fat cells throughout the body, both under the skin and around the delicate organs. That’s enough stored energy to walk briskly non-stop for 500–600 miles, or from London to Land’s End. The body also stores fat between the muscle fibres, generally holding about 2,000–3,000 calories, enough to walk briskly non-stop for 20–30 miles. So before we even start to consume food for energy, our bodies are holding on to an awful lot of energy in the form of stored fat.

Where the fat is stored creates quite distinctive body shapes. Storage of body fat around the middle, resembling more of an apple or ‘android shape’, is characteristic among males and is associated with a higher risk of cardiovascular disease. Storage of body fat around the hips and thighs, creating a more rounded pear or ‘gynoid’ shape, is the most common body type among pre-menopausal women. The role of hormones in the way we store fat differs between men and women and affects how each lose weight.

Two hormones are particularly associated with fat distribution. Lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL) directly affect whether we store fat or encourage it to be distributed in the blood and then burnt off. LPL tends to encourage fat storage, and HSL tends to encourage fat to be burnt off. The amount of LPL and HSL we have tends to vary between men and women, between individuals, in different areas of the body and at various stages of a woman’s life. Men tend to have more LPL in the belly and less HSL in the lower hip area. This creates the more pronounced apple or android body shape seen in overweight men, with more body fat distributed around the belly. Women tend to have more LPL in the hips and backs of the arms and less HSL in the upper body. This classically creates more of the traditional pear or gynoid shape. When women lose weight, they generally still have more LPL in the hips so retain a pear shape, even though they may be a smaller pear shape.

It therefore seems obvious that getting more HSL can be only a good thing for aiding weight loss. HSL is stimulated by the hormone epinephrine, and what is really exciting is that exercise causes greater amounts of epinephrine to be released, and as you get fitter your body becomes more adept at using even small amounts of epinephrine to burn fat. So that’s a great reason to get moving and keep moving.

A body that is significantly overweight or obese, however, will require higher amounts of epinephrine to stimulate fat-burning. For this reason it is vital that overweight people include gradual, progressive cardiovascular exercise into their weight-loss efforts. Walking is a fabulous way to do this.

The crucial difference between male and female fat loss is down to hormone receptors, which are located on the fat cell walls. There are two types of hormone receptor: alpha-receptors and beta-receptors. Alpha-receptors tend to inhibit fat breakdown while beta-receptors encourage it. Men and women don’t have the same amount of these crucial hormone receptors. Men tend to have more of the fat-busting beta-receptors and fewer of the fat-storing alpha-receptors in their abdomen, while women tend to have fewer beta-receptors and more alpha-receptors. The more beta-receptors there are in the abdomen, the easier it is to lose middle-age spread. So when a man loses weight, it will be easier for him to drop inches off the midriff area than it would be for a woman. Finally, the last infuriating piece of evidence that it’s easier for men to lose weight is that, even at rest, a man will be burning more calories than a woman. This is because their fat cells are smaller than women’s!