Question

Questions: Suppose that someone ate an excess of1000 kcal. How much of this 1000 kcal will become fat?Suppose that someone had a deficit of1000 kcal. How many grams of fat will be lost in order to generate the1000 kcal? What I've done so far I found thateach gram of fat contains9 kcal. So, a naive solution would be: An excess of1000 kcalwill become1000/9 = 111.11... gof fat.A deficit of1000 kcalwill cause the loss of1000/9 = 111.11... gof fat. This is naive, because it ignores that the body itself requires some calories for simply converting excess calories to fats, or for converting fats back to calories. In Quora, I found someone claiming that such conversion has a20%overhead for each direction. So, if I understand his answer, the better answer is: An excess of1000 kcalwill spend1000*.2 = 200 kcalas calorie-to-fat conversion overhead, leaving us with1000-200=800 kcalthat is going to be stored as fat. Since each fat gram contains9 kcal, we will eventually store800/9 = 88.88... gof fat from the1000 kcalexcess.Likewise, a deficit of1000 kcalwill also have a20%overhead. So, to get1000 kcal, the body will have to burn enough fat that gives1000 * 1.2 = 1200 kcal, which is1200 / 9 = 133.33... gof fat. But, the problem with this answer is two folds: It assumes that the overhead is20%. I couldn't find a study for this.It assumes that the overhead is symmetrical so that calorie-to-fat's overhead equals fat-to-calorie's overhead. I couldn't find a study to claim this symmetry.

Answer 1

Excess calorie intake leads to fat storage, while a calorie deficit leads to fat metabolism for energy, with the rough estimate being a 3,500 kcal deficit resulting in the loss of one pound of body fat. The efficiency and energy costs of these conversions are not universally fixed and can be influenced by various individual factors.

Step-by-step explanation:

The process of metabolizing calories and how it affects body weight is an integral part of understanding nutrition and health. When a person consumes more energy than they expend, the excess energy is stored as fat. For instance, if an individual requires 3000 kcal (12,000 kJ) per day and consumes an additional 1000 kJ (about 239 kcal), they will gain weight unless the extra energy is expended through physical activities like bicycling or other forms of exercise.

Conversely, if a person has an energy deficit by consuming fewer calories than they use, their body will metabolize stored fat to provide the necessary energy, resulting in weight loss. To lose one pound of body fat, a person must have a caloric deficit of approximately 3,500 kcal. However, the exact conversion of dietary calories to stored fat and the metabolic cost of converting stored fat back to usable energy can vary and is not straightforward due to factors such as individual metabolic rates and the thermic effect of foods.