Why does simply counting calories often fail for weight loss? A scientific analysis of the reasons and the correct approach.

Firstly, the calorie data you typically find in apps, websites, books, and other media is only an average value measured in a laboratory and cannot accurately represent the actual calorie content of the food. Just as no two pieces of pork have the same fat content, their calorie content will naturally differ. Besides fresh ingredients, the calorie information on food labels often has significant errors. The U.S. Food and Drug Administration (FDA) allows a 20% margin of error in calorie labeling. This means a snack labeled as 200 kcal might actually contain only 160 kcal or as much as 240 kcal. The difference in calories for the same food can easily exceed 100 kcal.

Secondly, the processing method also has a significant impact on the actual absorption rate of calories. Frying, boiling, stir-frying, steaming, and other cooking methods all affect the calorie content of food. For example, a raw pumpkin has 23 kcal, while a fried pumpkin has 103 kcal. Furthermore, cooked food provides more absorbable calories than raw food; for instance, you absorb more calories from a medium-rare steak than from a rare steak.

Thirdly, individual absorption rates vary greatly. Calorie absorption is usually measured by laboratory instruments, but humans are not machines. Each person's digestive capacity, absorption capacity, metabolic rate, and gut microbiome are different, all of which affect the actual calorie absorption by the body. For example, people with a higher proportion of "obesity-related bacteria" (Firmicutes) in their gut absorb an average of 150 kcal more per day than normal individuals.

Finally, when calculating calories, almost everyone unconsciously underestimates their calorie intake. In other words, the actual calorie intake is far greater than what they calculate. Even professional nutritionists underestimate calorie intake by an average of 30% when calculating it.

Firstly, just as the calorie information found on websites and other sources is inaccurate, the calorie expenditure values ​​displayed on fitness apps, treadmills, and fitness trackers are also average values ​​based on laboratory or big data statistics, with errors ranging from 20% to 80%, and do not correspond to individual actual consumption.

Secondly, the values ​​you calculate for your basal metabolic rate using formulas are also not accurate. Individual differences in people are significant; body fat percentage, organ size, basal body temperature, and genetic differences all affect each person's basal metabolic rate. Even a single person's basal metabolic rate is not a constant value; it changes depending on hormone secretion, emotions, stress levels, and lifestyle. For example, during menstruation, hormonal changes in women significantly affect their basal metabolic rate, with calorie fluctuations of up to 100 kcal being considered normal; staying up all night also directly affects basal metabolic rate, resulting in a 5% to 20% reduction in calorie expenditure the following day.

Furthermore, when calculating daily calorie expenditure, people often overlook the thermic effect of food. Simply put, the body requires extra energy to chew, digest, break down, and absorb food. This phenomenon is the thermic effect of food. Protein-rich foods have the highest thermic effect, at 20%–35%; carbohydrates are next, at 5%–15%; and fats have the lowest, at 3%–5%.

Moreover, calorie expenditure is also affected by the environment. The average metabolic rate is higher in winter than in warmer seasons; calorie expenditure is also higher at high altitudes than at sea level because the lower temperatures at high altitudes require the body to expend more energy for heat.

Genetic differences also affect calorie expenditure, which is the main reason why it's impossible to accurately calculate how many calories each person burns.

Therefore, weight loss methods based solely on calorie counting often end in failure and rebound; it's not a long-term effective weight loss method. Food calories should only be used as a rough guide, because the human body is far more complex than you imagine, and calorie expenditure cannot be calculated using simple formulas. When people eat, they don't just consume calories, but also nutrients that are even more important to the body. Therefore, you should focus not on the number of calories, but on the source of those calories—the quality of the food. Consider this: which is healthier and more conducive to weight loss, 1000 kcal of candy or 1000 kcal of vegetables? The answer is obvious. Therefore, weight loss methods that only focus on calorie intake and expenditure, without considering food type, digestion speed, energy utilization, nutritional content, and the impact on hormones and metabolism, are extremely inefficient.