During the first few hours of a fast, your body gets its fuel from glycogen stores in your liver and muscles; the glycogen is broken down into glucose. Once the glycogen is gone, however, your body breaks down a mix of both fat and muscle to provide it with the fuel it needs.
During fasting, the body starts to break down muscle for energy, which can lead to a loss of muscle mass. This is because the body doesn't have sufficient energy sources, such as glucose from carbohydrates, to sustain its activities, so it turns to muscles for fuel.
Fat burning typically begins after approximately 12 hours of fasting and escalates between 16 and 24 hours of fasting.
Fat burns first. Work out for a week and you gain muscle, lose fat no vice-versa. In cases of starvation, fat is used first, mainly because it's a lighter substance and easier to break down to energy.
It's made up of multiple linked glucose molecules, the simple sugars in our blood that are derived from digestion. The body can burn either sugar or fat for energy, but using sugar is both faster and easier, so it uses that first.
Your muscles first burn through stored glycogen for energy. “After about 30 to 60 minutes of aerobic exercise, your body starts burning mainly fat,” he explains. (If you're exercising moderately, this takes about an hour.) Experts recommend at least 30 minutes of cardio two to three times a week.
Mostly, losing weight is an internal process. You will first lose hard fat that surrounds your organs like liver, kidneys and then you will start to lose soft fat like waistline and thigh fat. The fat loss from around the organs makes you leaner and stronger.
You may have difficulty losing weight with intermittent fasting if you're eating too many calories, too few calories, or don't have a balanced diet.
Fasting for 12 hours a day
According to some researchers, fasting for 12 to 14 hours can cause the body to turn its fat stores into energy, which releases ketones into the bloodstream. This should encourage weight loss. This type of intermittent fasting plan may be a suitable option for beginners.
Your body may go into ketosis after just 12 hours of not eating, which many people do overnight before they "break fast" with a morning meal. (A midnight snack obviously sabotages this process.) A keto diet keeps you in ketosis for much longer time periods because you avoid carbohydrates, which supply glucose.
Fasting is a powerful tool for targeting and reducing belly fat. It works by shifting your body's metabolism from burning sugar to burning fat as its primary source of energy. This metabolic shift is what leads to fat loss, particularly in the abdominal area.
When on a weight loss journey, lack of protein is a huge culprit of muscle loss. “Our bodies don't store protein like other nutrients, so it's important to eat the right amount every day,” says Kate. “Everybody is different and will have different protein requirements.
A more reliable indicator is simply looking in the mirror. Many of us don't enjoy gawping at ourselves in the mirror but it's a good indicator of your fat burning prowess. As you become better at fat burning, you should notice less fat stored around the stomach, hips, legs and shoulders.
Reduce Your Health Risks
Obesity increases your risk for many health problems. Losing the extra weight can help eliminate those health problems or lower your odds for them. Weight loss can reduce your blood pressure and cholesterol. It can also slash risk for diabetes, heart disease, stroke, and osteoarthritis.
Generally speaking, the first place men typically lose weight is the belly, while women tend to lose weight all over, but may hold onto weight in the thighs and hips more so than men, Dr. Block says.
The Science of Fat Loss
Think of it like a balloon losing air—it deflates, but doesn't disappear immediately. Over time, your body adjusts, but the jiggly feeling can be a temporary step along the way.
You may notice when you start to lose weight that you'll need to urinate more often. That's because your body is attempting to get rid of those byproducts. Drinking more water can help encourage this process, and may even help boost your metabolism.
After prolonged periods of starvation this store of glycogen runs out, and the body then starts burning fat reserves and consuming muscle and other tissues and uses the proteins within muscle tissue as a fuel source, which results in muscle mass loss.
Unhealthy eating is the biggest driver of big bellies. Too many starchy carbohydrates and bad fats are a recipe for that midsection to expand. Instead, get plenty of veggies, choose lean proteins, and stay away from fats from red meats. Choose healthier fats in things like fish, nuts, and avocados.