"All foods contain calories, and all calories are either used by your body for immediate energy, stored away as glycogen as a source of future energy or turned into fat — depending on how many calories you eat during a period of time," explains Leslie Ramirez, clinical dietitian at Houston Methodist.
Excess calories are stored throughout your body as fat. Your body stores this fat within specialized fat cells (adipose tissue) — either by enlarging fat cells, which are always present in the body, or by creating more of them.
So how long does it take for excess carbohydrates to turn to body fat? Once a meal is consumed, your body either uses the calories as fuel, or stores the calories in fat cells to be used a later time. Within four to eight hours from the beginning of a meal, your body begins to store consumed calories as fat.
Eating an excess of empty calorie foods leads our bodies to store additional calories as fat, leading to weight gain [2]. Note that eating empty calories as part of a balanced or overall healthy eating approach will not cause spontaneous weight gain.
Any time you eat, your body uses some of the calories you consume for energy. The rest are stored as fat. Repeatedly consuming more calories than you burn can cause you to become overweight, and eventually, obese.
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.
One of the primary reasons that undereating can lead to weight gain is because consuming too few calories can cause your resting metabolic rate to slow down. This means you may burn fewer calories throughout the day.
When the supply of energy—the number of calories consumed in foods—exceeds the body's immediate needs, the body stores the excess energy. Most excess energy is stored as fat. Some is stored as carbohydrates, usually in the liver and muscles. As a result, weight is gained.
If the ingredients contain oil, butter, and any type of fat, then it still has calories. For example, a typical zero calorie serving for an 8oz bottle of spray butter is 5 sprays.
Muscle helps keep up the rate at which you burn calories (metabolism). So as you lose weight, your metabolism declines, causing you to burn fewer calories than you did at your heavier weight. Your slower metabolism will slow your weight loss, even if you eat the same number of calories that helped you lose weight.
So if you lose 1lb (0.45kg) a week you could hope to reduce your waistline by an inch after four weeks. Dieticians advise that if you eat 500 calories less than your daily requirement you will lose about 1lb every seven days (expect some variation from person to person).
FACT: Research has shown that vomiting cannot get rid of all the calories ingested, even when done immediately after eating. A vomit can only remove up to about half of the calories eaten - which means that, realistically, between half to two thirds of what is eaten is absorbed by the body.
Fat burning typically begins after approximately 12 hours of fasting and escalates between 16 and 24 hours of fasting.
"Empty calories can provide some immediate energy, but they can't be used to build muscle, supply vitamins, promote a sense of fullness or provide any other nutritional benefits," says Ramirez. "And any empty calories not used for energy will be stored as fat."
Dr. David Katz, reports in "O, the Oprah Magazine," that the body begins to store consumed calories as fat within four to eight hours from the beginning of the meal. As you consume these calories, the body automatically stores the first 1,000 calories within the liver and muscles for immediate energy reserves.
If you're asking yourself, “Why am I gaining weight when I barely eat,” several factors may be at play. Your body may be holding onto fat stores if your eating habits are inconsistent or restricted. Or, your weight gain may be the effect of a sedentary lifestyle, medical condition, or long-term stress.
She revealed that white bread, high-sugar cereals, sodas, and ultra-processed snacks are some of the ones to steer clear of.
Your body composition may be another reason why you are still gaining weight while in a calorie deficit. If you have a higher body fat percentage and lower muscle mass, then you are probably burning fewer calories than if you had more muscle mass.
“This is a frequent myth, but no, just because food moves through your body quickly does not necessarily mean you have a fast metabolism,” says Megan Hilbert, MS, RDN, a registered dietitian at Top Nutrition Coaching based in Madison, Wisconsin.
Why does metabolic rate slow down for women? Over time, studies have shown that metabolic rate (how fast we burn calories) starts to slow down by 2 to 3 percent each decade, beginning in our 20s. It becomes more noticeable between ages 40 and 60.