Is calorie deficit really the only way to lose weight? What to know about risks, according to a dietitian

Welcome to Ask A Dietitian, a series where Yahoo Canada digs into food trends and popular nutrition questions with registered dietitian Abbey Sharp.

This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. Contact a qualified medical professional before engaging in any physical activity, or making any changes to your diet, medication or lifestyle.

In a world obsessed with quick fixes and fad diets, the concept of a calorie deficit stands out as a cornerstone in the weight loss conversation. But is it the be-all and end-all way to shed unwanted pounds?

Canadian registered dietitian Abbey Sharp gave Yahoo Canada the scoop on whether you really need to be in a calorie deficit to lose weight — and how it works. Here's what you need to know.

What is a calorie deficit and is it essential for weight loss?

A calorie deficit occurs when you consume fewer calories than your body uses. According to Sharp, this fundamental mechanism forces the body to draw on its stored energy reserves, typically fat, to make up for the shortfall, leading to weight loss. In simple terms: you burn more calories than you intake through food and drink.

When a person maintains a calorie deficit over time, that use of stored fat leads to a loss of body fat, aka weight loss. So yes, you do need to be in a calorie deficit to lose weight, Sharp said, adding it's "thermodynamics."

However, Sharp emphasized a critical distinction that often gets blurred in mainstream discussions: "There's a significant difference between a calorie deficit and calorie counting." Calorie counting is just one of many strategies to achieve a calorie deficit, she claimed.

Alternative methods, such as intermittent fasting or adopting the plate method (filling half the plate with vegetables), can also result in a calorie deficit without the need for meticulous calorie tracking.

"Mindful eating is another way that some people may achieve a calorie deficit," Sharp said. "Or using my hunger crushing combo method, which really focuses on building meals with fiber, protein and healthy fat."

What else influences weight loss?

Weight loss is influenced by a myriad of factors beyond simple calorie equations. Metabolic rate, age, sex, body composition and hormone levels all play roles in how effectively a person loses weight, Sharp said.

"Your metabolism is your body's process of converting food into energy, and some folks just have a faster metabolism. So they're burning more calories at rest and during physical activity," she explained. "We all have our kind of genetically determined body shape and size. So some folks have more muscle mass naturally... and muscle tissue is more metabolically active than fat tissue, so it's going to burn more calories at rest."

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Hormones (especially insulin, leptin, ghrelin, cortisol and thyroid hormones) are important in regulating our appetite and energy balance."All of those can affect our hunger, satiety and our body's ability to burn fat," Sharp said.

Certain conditions (like hypothyroidism or PCOS), and medications (antidepressants, antipsychotics, corticosteroids) are going to make it more difficult to lose weight. The gut microbiome, an area of particular interest to Sharp, can also significantly impact metabolism and nutrient absorption.

Are there any risks to being in calorie deficit?

While a calorie deficit is necessary for weight loss, a person's caloric needs will change as they lose weight. This means that eventually, once weight is lost, you won't need to keep being in a deficit.

"A healthy calorie deficit is one that translates to around one to one-and-a-half pounds of weight loss per week. Usually, that's a 20 per cent deficit or around 500 calories [a day]," Sharp explained. "If you're dieting and losing weight actively, you're going to get to a point where hopefully, you don't want to be in a calorie deficit anymore."

Maintaining such a state for an extended period can have adverse effects, however. Sharp cautioned that prolonged calorie deficits can lead to loss of muscle mass, nutrient deficiencies, hormonal imbalances and even weakened immune function. In women, it can also impact reproductive hormones, putting them at risk of fertility issues.

What to know about misinformation around calorie deficits

In an era where wellness influencers often dispense dietary advice, Sharp raised concerns about misconceptions with calorie deficits. One is the notion that a one-size-fits-all calorie intake, such as 1200 calories per day, is suitable for everyone.

"For most adults, this is way too low," Sharp warned, adding it can be "dangerous" even. "These are the caloric needs of a three-year-old toddler. It's not going to be enough for you to be able to sustain long term."

Sharp's advice is clear: steer clear of generalized diet recommendations from non-professionals and seek guidance from a registered dietitian to determine safe and effective calorie deficits.

Why calorie deficits are a tool, not a rule

So, how should one approach the concept of calorie deficits in the context of weight loss? Sharp advocated for a nuanced perspective. "You need to find a method of weight loss that allows you to achieve a modest, safe calorie deficit in the most enjoyable way possible," she advised.

Whether through mindful eating, focusing on nutrient-dense foods, or incorporating physical activity, there are multiple pathways to achieve a calorie deficit. The key is to adopt a strategy that is sustainable, enjoyable, and promotes your overall health.

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