Counting Calories to Lose Weight: What Goes Wrong with the Deficit?

Why 1,500 Calories With Bread Don't Lead to Weight Loss, But 1,700 Without Bread Do

The case is recounted by the person who lived it and gets to the heart of the matter. On a diet of 1,500 calories that included bread, pasta, and some sugary or floury products, weight remained stable or increased slightly. On 1,700 calories and without bread, pasta, sugar, or flour, the scale consistently went down. Same person, same activity, more food, and fewer kilos. When mentioned to a nutritionist, she suggested that perhaps the person was moving more. They were not moving more.

The episode encapsulates a debate that has been ongoing for years: is counting calories enough to lose weight, or does the body play by different rules? Energy deficit exists. The question is whether it's the only factor that matters.

Caloric Deficit Isn't Debatable, But Measuring It Is Difficult

Energy is neither created nor destroyed. To lose fat, one must expend more than is ingested, a point on which almost all currents agree. The disagreement begins with the calculator. Daily expenditure estimates are, in the words of critics, very rough approximations: patients aren't asked about their body temperature, even though maintaining 36 or 37 degrees Celsius is one of the most energy-consuming activities. If expenditure cannot be precisely measured, neither can the deficit.

Added to this is another objection. The idea that the body utilizes all ingested calories equally clashes with those who argue the opposite: the same number of kilocalories can be absorbed and metabolized differently depending on the food. Two servings with the same label don't end up the same on the scale.

Why Do Two 2,000-Calorie Diets Yield Different Results?

This is the most frequently repeated thought experiment. 2,000 calories of pasta, bread, sweets, and fried foods versus 2,000 calories of vegetables, meats, fish, eggs, and nuts. Same total, different expected result. The explanation offered involves insulin, described as the body's warehouse keeper: it collects sugar from the blood and stores it. If glycogen stores are always full due to the continuous trickle of refined carbs, the fat oxidation pathway becomes blocked.

The most cited evidence comes from a study with mice. Several groups were fed diets identical in calories and macronutrients, varying only in texture, from granules to powder. Those who ate the powder gained significantly more weight across all compositions, with a much higher insulin response. This seemingly anecdotal detail provides ammunition to those who argue that food form matters as much as its calorie count.

BMI Doesn't Distinguish Between an Obese Person and an Athlete

Losing weight isn't the ultimate goal, even though language might suggest otherwise. The Body Mass Index has statistical value for populations and very little for individuals: two people with the same BMI could be an obese person and an elite athlete. Differences in bone density, hydration, and muscle mass invalidate the calculation. An indicator that lumps an athlete and an overweight patient into the same category is not useful for making decisions, yet it dictates a large part of medical consultations.

Keto, Fasting, and the "Keto Flu" Week

Personal accounts are accumulating. One describes how they went from 85 kilos and 20% body fat to 81 kilos and 16.5% with a low-carbohydrate diet and fasting for 22 to 24 hours, a single meal per day. Another claims to have lost two belt notches with a paleo-style diet, eating more than ever. When giving up refined foods, they warn, you go through an initial week of weakness, dizziness, and bad mood: the keto flu. There's also the social cost, as in a bar, almost everything ordered is hyper-sugary.

The history of bodybuilding adds context. It's said that bodybuilders of the golden era stayed close to their competition weight almost year-round and only lost four or five kilos to compete. Today, according to the same narrative, many carry tens of kilos more.

What the Label Doesn't Say

Distrust isn't solely aimed at calories; it targets the packaging. Digestive biscuits are marketed as digestive when the packaging itself clarifies they are not, and decades of breakfasts have been built on this confusion. Critical eyes also point to sugary drinks, shakes, and processed foods with corn syrup as the real drivers of overweight, ahead of meat.

There remains a piece of data that no one quite fits. A kilo of fat under the skin is equivalent to about 9,000 calories that the body stores for lean times. If it receives the calories it needs every day, why would it mobilize reserves? No one has yet provided a definitive answer to this question.