We’ve all been there. You’re eating less, moving more, yet the scale refuses to budge.
In a world obsessed with quick fixes and crash diets, calorie deficit has long been a go-to weight loss strategy. But according to Jill Brown, a certified master health coach and nutrition expert, it’s not always as simple as it sounds.
“While this can and does work a lot of the time, people get really frustrated when it appears they are doing this but it’s not working,” Brown told The Post. “The problem lies in that most people don’t really know what a calorie deficit really is.”
Calories in: the hidden pitfalls
We all need calories to fuel our bodies, but that magic number isn’t set in stone. Women typically need between 1,800 and 2,400 daily to maintain their weight, while men require around 2,000 to 3,000, according to the 2020–2025 Dietary Guidelines for Americans.
The basic theory behind a calorie deficit is simple: Burn more calories than you consume, and your body will dip into its fat reserves for energy, leading to weight loss over time.
Brown said this concept is known in fitness circles as CICO, or “calories in vs. calories out.”
But figuring out how many calories you’re actually consuming is where things get tricky. In fact, a landmark study found that people miscalculate how many calories they take in by as much as 1,000 calories a day.
And it’s not just about your portion sizes. Brown noted that the Food and Drug Administration allows nutrition labels to be up to 20% off, meaning the calorie counts on packaged foods — and even at restaurants — could be way higher (or lower) than advertised.
The confusion doesn’t end there. Brown said fitness trackers, those fancy gadgets we love to rely on to measure how many calories we’re burning while exercising, aren’t foolproof either.
A study from the Stanford University School of Medicine compared seven different wrist-worn trackers and found that the most accurate calorie estimates were off by 27%, while the least accurate was 93% off.
To complicate things even further, not all calories are digested the same way.
Brown said the body absorbs fewer calories from certain foods, particularly those high in fiber, like nuts, compared to more processed foods like white bread.
“Not everybody absorbs the same amount of calories either, which may have a lot to do with the diversity of our gut biomes,” she said. “So unless you live in a metabolic ward laboratory, calorie counting is not always accurate.”
Calories out: Why the deficit doesn’t always work
Even if you’ve nailed your calorie intake, creating a deficit doesn’t always lead to weight loss. According to Brown, the issue is multifaceted, with several factors influencing how many calories you burn.
Take hormones, for example.
“Stress can trigger hunger hormones that cause us to snack more and crave more high calorie comfort foods, as does lack of sleep,” said Brown. “Drops in estrogen and testosterone during menopause also seem to trigger hunger hormones.”
Hormones also affect how many calories your body burns. “Having a low functioning thyroid leads to less calories out,” Brown explained, noting that this small, butterfly-shaped gland is the “master regulator” of our metabolism.
Age is another major player. As we get older, metabolism generally slows down — and so do our activity levels.
“Doing fewer overall activities like cooking, cleaning, chores and just running around like we did when we were younger leads to less calories out,” said Brown. “Pain from injuries and illnesses also lead to less spontaneous movement.”
And let’s not forget about medications. Brown noted that some drugs can mess with your hunger, alter your gut biome and even slow your metabolism, making it that much harder to create a calorie deficit.
