The weight management basic rules from energy prospective are simple - it is all about the balance. The energy comes in and comes out. If these numbers are balanced, the weight remains stable. Negative balance results in the weight loss. Positive balance results in the weight gain.
Energy is measured in Calories.
Daily calories expenditure = Basal Metabolic Rate + Physical Activity
Basal Metabolic Rate (link) is an amount of energy burnt by human body just to maintain the physiological functions, like blood circulation, breathing, maintaining body temperature etc. It may vary greatly from person to person with the same dimensions and level of activity, but it is never zero. In other words, no matter how low the basal metabolic rate is, the body will always lose weight when there is a sufficient energy deficit. High Basal Metabolic Rate is a reason why some of your skinny friends might eat everything and stay lean.
Average Basal Metabolic Rate in North America for women is 1500 cal/day and for men is 1700 cal/day
Total average calories expenditure in North America is around 2000 cal/day for women and 2200 cal/day for men.
Energy deficit around 500 cal/day usually results in 1-2 pound/week weight loss.
CNN. Nov 8 2010. For 10 weeks, Mark Haub, a professor of human nutrition at Kansas State University, ate one of these sugary cakelets (twinkies) every three hours, instead of meals. To add variety in his steady stream of Hostess and Little Debbie snacks, Haub munched on Doritos chips, sugary cereals and Oreos, too.
His premise: That in weight loss, pure calorie counting is what matters most -- not the nutritional value of the food.
The premise held up: On his "convenience store diet," he shed 27 pounds in two months.
For a class project, Haub limited himself to less than 1,800 calories a day. A man of Haub's pre-dieting size usually consumes about 2,600 calories daily. So he followed a basic principle of weight loss: He consumed significantly fewer calories than he burned.
His body mass index went from 28.8, considered overweight, to 24.9, which is normal. He now weighs 174 pounds.
Energy deficit can be created either by restricting the amount of consumed energy or by increasing the amount of energy spent, or both. Exercise without proper dietary adjustments might not result in any significant weight loss as people who exercise more, often may consume extra food to compensate for the burnt calories.
The common practice is to target the consumed energy to 1000-1200 cal/day for women and 1200-1500 cal/day for men of average complexity, which should result in weight loss around 1-2 pounds a week for most people.
There is usually no benefit in going below 800 cal/day diet.
Counting calories work. Weight watchers diet is well known with incredible results.
Unfortunately, it works for many, for others this is also might be a way to regain pounds as soon as they stop dieting and counting calories. Hunger is a powerful self preservation biological instinct and some people find it difficult to overcome it for too long.
If you want to have a healthy balanced metabolism and appetite, if you want to be able to rely on your instincts instead of calculator to decide how much food your body needs, then we have to go on and read more about food quality to learn more how different macronutrients affect our appetite.
P.S.
The human body’s metabolic rate decreases nearly 2 percent per decade after age 30. Changes in body composition, including reduced lean muscle mass, are mostly responsible for this decrease. The most dramatic loss of muscle mass, and consequential decline in metabolic rate, occurs between 50 and 70 years of age. Loss of muscle mass is the equivalent of reduced strength, which tends to inhibit seniors from engaging in sufficient physical activity. This results in a positive-feedback system where the reduced physical activity leads to even more muscle loss, further reducing metabolism.
There are several things that can be done to help prevent general declines in metabolism and to fight back against the cyclic nature of these declines. These include eating breakfast, eating small meals frequently, consuming plenty of lean protein, drinking water to remain hydrated, exercising (including strength training), and getting enough sleep. These measures can help keep energy levels from dropping and curb the urge for increased calorie consumption from excessive snacking. While these strategies are not guaranteed to maintain metabolism, they do help prevent muscle loss and may increase energy levels. Some experts also suggest avoiding sugar, which can lead to excess fat storage. Spicy foods and green tea might also be beneficial. Because stress activates cortisol release, and cortisol slows metabolism, avoiding stress, or at least practicing relaxation techniques, can also help.