7.8 Why You’re Not Losing Weight: Myths vs. Realities

If you are in a genuine caloric deficit, you will lose weight. The laws of physics do not have exceptions for your metabolism, your genetics, or the time you eat dinner. When weight loss stalls, the cause is always a discrepancy between perceived intake and actual intake, or between perceived expenditure and actual expenditure. This section addresses the most common myths people use to explain their plateau—and the uncomfortable realities behind them.

The Myths

These are popular explanations for weight loss failure that do not withstand scientific scrutiny.

“Sugar and carbs make you fat.” No. A caloric surplus makes you fat. Carbohydrates and sugar are the most commonly blamed macronutrients, but if your total energy intake is below your expenditure, you will lose weight regardless of carb intake. The demonisation of sugar has more to do with the fact that sugary foods tend to be hyper-palatable and easy to overeat, not because sugar has some unique fat-storing property.

“Insulin is the enemy.” Insulin is a storage hormone—it facilitates the uptake of nutrients into cells. But insulin does not override energy balance. Hall et al. (2015) conducted a tightly controlled metabolic ward study comparing an isocaloric low-fat diet to a low-carb diet and found that despite significant differences in insulin secretion, the low-fat diet actually produced slightly greater body fat loss [9]. Insulin is a response to energy intake, not the cause of fat gain.

“You need a specific diet (keto, paleo, carnivore, vegan).” All named diets that produce weight loss do so by creating a caloric deficit—whether intentionally (through portion control) or incidentally (by eliminating entire food groups, which reduces options and therefore intake). Meta-analyses consistently show that when calories and protein are equated, there is no meaningful difference in body composition outcomes between diets [10]. The best diet is the one you can adhere to.

“Eating at night makes you fat.” Your body does not know what time it is. A calorie consumed at 9 PM has the same energy content as a calorie consumed at 9 AM. The association between late-night eating and weight gain exists because people who eat late tend to eat more total calories (snacking in front of the TV, for example), not because nighttime calories are metabolised differently.

The Realities

These are the actual reasons people fail to lose weight, backed by consistent evidence:

Underestimating food intake. This is the number one cause of unexplained weight loss failure. Studies using doubly labeled water (the gold standard for measuring energy expenditure) consistently show that people underreport their food intake by 20–50%, with higher BMI individuals underreporting more [11]. The salad that “couldn’t have been more than 300 calories” was actually 600 because of the oil, cheese, croutons, and dressing. The “handful” of nuts was 400 kcal. The cooking oil you didn’t count was 300 kcal. It adds up.

Overestimating energy expenditure. Fitness trackers and cardio machines routinely overestimate calories burned. Studies have shown that popular wrist-worn devices overestimate energy expenditure by 27–93% depending on the activity [12]. “I burned 600 calories on the elliptical” is almost certainly false—the real number is probably 250–350.

Weekend blowouts. A disciplined 500 kcal/day deficit from Monday to Friday creates a weekly deficit of 2,500 kcal. Two days of eating 1,250 kcal above maintenance on the weekend (a very easy thing to do with restaurant meals, alcohol, and relaxed eating) wipes out the entire deficit. Net result: zero progress over the week.

Binge-restrict cycles. Rigid, all-or-nothing dieting creates a psychological pattern: restrict aggressively → feel deprived → “break” the diet → binge → feel guilty → restrict harder. This cycle is self-reinforcing and prevents sustained progress. A moderate, flexible approach with built-in dietary freedom (the 80/20 guideline from Section 7.6) breaks this pattern.

Liquid calories. Juice, soda, alcohol, sweetened coffee drinks, and smoothies contribute calories with minimal satiety. A large latte with syrup can be 400 kcal. A “healthy” fruit smoothie can be 500 kcal. These calories are real, they count, and they are extraordinarily easy to forget.

If you genuinely believe you are eating 1,500 kcal/day and not losing weight, the most likely explanation—by far—is that you are not actually eating 1,500 kcal/day. Before blaming your thyroid, your metabolism, or your genetics, weigh your food with a kitchen scale for one week and log every single thing that enters your mouth, including oils, sauces, drinks, and the “bites” you take while cooking. The answer is almost always in the data.