Are fasting, calorie counting, and deprivation slowing your metabolism and preventing you from meeting your weight loss goals?

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.

Jill Brown, a certified master health coach and nutrition expert, told The Post that this concept is known in fitness circles as CICO, or “calories in vs. calories out.”

But what does it mean if you’re counting calories and not getting results?

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. 

Experts agree that weight loss happens when the body is in a calorie deficit; however, determining how many calories you consume and what equals a deficit is slippery math.

In fact, a landmark study found that people miscalculate how many calories they take in by as much as 1,000 calories a day. 

“When people tell me they’re in a calorie deficit, I ask them, ‘How do you know?’ They can’t really answer.  The truth is, if you’re not losing weight, you’re simply not in a calorie deficit,” said Brown.

Brown explained that part of the disconnect between counting calories and losing weight is that most folks don’t know their exact resting metabolic rate or RMR.

“Home smart scales are unreliable, and I see many people using this as their primary measurement,” she said.

“Getting a DEXA scan that measures your body composition is your best option. The next best would be an InBody machine. These machines will give you an estimate of your RMR, or how many calories your body burns a day doing nothing.”

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These machine-generated estimates are based on body weight, muscle mass, bone mass, and fat mass, providing a more accurate picture of your caloric expenditure.

Brown explained that online calculators only factor in age, height, weight, and self-reported activity level, leaving ample room for error.

“They can be off by as much as 20-30% in normal, young, healthy people. They may be even farther off for older people or those who have illnesses or obesity. 

“Not to mention, none of these calculators factor in medications or gut health status.”

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.

For those looking to lose and target a calorie deficit without integrating technology, Brown recommends a good old-fashioned food diary.

“I have my clients honestly log everything they eat (even little sips and licks) for a good week or two and weigh in daily. If the scale is still the same at the end of the week, they’re burning as many calories as they’re taking in,” she said.

According to Brown, once that baseline is established, it’s easy to find ways to reach a deficit.

“Eat a little less (think smaller portions, skipping snacks or not having desserts), do a little more physical activity, and get good sleep, and you’ll be in a deficit,” she said.

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While a deficit is a healthy goal, Brown says deprivation is not only ineffective but counterproductive.

“Extreme calorie deficits only work in the short term because they place a huge amount of stress on the body,” said Brown.

“If you try to do this for weeks or months, your hunger hormones will go nuts and compel you to eat back all those calories. If you continue to fight through it, your body will respond by slowing down its metabolic rate.

“If you continue to eat an extremely low-calorie diet, your body will simply burn less calories to preserve energy. You will even burn less calories when you exercise.”

Brown also noted that regular exercise suppresses hunger, but over-exertion amplifies it. Thus, she recommends people find a sweet spot between challenge and exhaustion that works for them.

She counts rest and relaxation as additional requisites for weight loss: “Getting quality sleep while managing stress prevents those sneaky hunger hormones from derailing you when you don’t realize it.”