From headache to heart disease: 7 reasons why you shouldn’t be intermittent fasting for weight loss

Who cares to eat when fasting is trending!

Intermittent fasting has become a widely popular method for weight loss and improved metabolism, celebrated by health influencers, celebrities, and tech leaders alike. The simplicity of eating within a set time window, skipping meals like breakfast, and losing weight as a consequence sounds too good to pass up.

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But here’s the kicker you should know before jumping on the fasting bandwagon: the science behind IF is still evolving, and cautionary signs are emerging.

Intermittent fasting (IF) is the practice of cycling between eating periods and fasting, with popular methods like 16:8, where you eat during 8 hours, fast for 16, or the 5:2 approach, where you eat normally for five days, and intake very limited calories on the rest of two days.

Although this dieting pattern has become trendy and has been approved by social media, it’s important to understand the lesser-known, everyday signs and long-term risks that come with extreme eating schedules.

In fact, a recent research analyzed data from more than 19,000 adults, and found that those who confined their eating to less than eight hours a day faced a 135% higher risk of dying from cardiovascular disease, issues with the heart and blood vessels, than people who ate over 12-14 hours.

And that’s not where the perils end.

So, what other side effects does this trendy diet pattern come with?

What do we gain from eating food? The fuel that drives and sustains us throughout the entire span of the day. Skipping meals or eating within tightly restricted time frames can lead to low blood sugar, dehydration, or electrolyte imbalance. People often report headaches, lightheadedness, irritability, lethargy, and mental fog, even in the short term. As your body adjusts, you may feel constantly drained, hampering work, concentration, and mood stability.

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A major study of over 20,000 US adults found that those who confined their eating to under 8 hours a day had a 91% higher risk of death from cardiovascular disease compared to those spreading meals across 12-16 hours. A separate long-term study raised concerns of a 135% increase in heart-related death risk for similar restrictive patterns. Doctors warn especially people with existing heart conditions to steer clear of these extreme fasting schedules.

If you compress your food intake into just a few hours or restrict calories heavily, it’s easy to miss vital nutrients, especially protein, vitamins, and minerals. This is particularly risky for older adults, who may then lose too much weight, experience muscle wasting, lower energy, weakened immunity, and poorer bone health. Moreover, though intermittent fasting can promote fat loss, research shows that it may also lead to significant loss of lean body mass, muscles we need for strength, metabolism, and daily energy. Fitness experts warn that this can make exercise harder and slow recovery.

You can’t go under-eaten and hungry forever, right? While fasting may reduce calorie intake overall, it can backfire. You might feel driven to binge once the fasting window ends. Hunger hormones and your brain’s reward center may go into overdrive, leading to overeating and slowed metabolism. Over time, this cycle can harm weight-loss efforts and metabolic health. Furthermore, studies have shown a strong link between intermittent fasting and disordered eating, including bingeing, food cravings, guilt, and anxiety, especially among teens and young adults.

For adolescents and young adults, intermittent fasting can be a slippery slope. Fasting for extended periods (e.g., more than 16-18 hours) may increase the risk of gallstones, as the gallbladder doesn’t empty regularly. It may also contribute to metabolic stress, which could undermine long-term health. In one Canadian study of over 2,700 teens and young adults, women practicing IF were more prone to disordered eating behaviors compared to others. Combining IF with restrictive diets (like low-carb) raised risks even further, leading to stricter food cravings and binge patterns. Unsurprisingly, health professionals caution using IF only with careful screening and guidance.

Skipping meals, especially early in the day, can trigger stress responses. Hormones like adrenaline and cortisol may surge, potentially raising blood pressure or disturbing metabolic balance. Skipping breakfast, which is a common IF practice, may coincide with the body’s natural high-alert morning state, adding further strain to the heart.

Many people find it hard to continue IF. For individuals recovering from or prone to eating disorders, fasting may be particularly harmful. It can reinforce damaging cycles and hinder recovery. Additionally, studies show dropout rates up to 38% in fasting groups, suggesting poor long-term adherence. Without consistent discipline, the cycle of fasting and rebound eating can cause frustration, weight variability, and stress.