Unpacking Fad Diets: Keto, Paleo, Fasting – Do They Work?

 

Fad diets come and go, but a few trendy eating plans have dominated conversations in recent years. Chances are you know someone who swears by the ketogenic (“keto”) diet, sings the praises of the paleo diet, or schedules their meals around intermittent fasting. These diets promise weight loss and health benefits by breaking the mould of conventional eating. But do they really live up to the hype? In this article, we unpack the keto, paleo, and intermittent fasting diets – how they work, what the science says about their effectiveness, and whether they’re truly the magic bullets for weight loss and health that some proponents claim. We’ll take a warm, accessible look at the evidence so you can make informed decisions about these popular diet trends.

The Ketogenic Diet: Carbs Out, Fat In

The ketogenic diet is a very low-carbohydrate, high-fat diet. By drastically cutting carbs and upping fat intake (often 70–80% of daily calories from fat), the goal is to push the body into ketosis. In ketosis, the body burns fat for fuel instead of its preferred energy source, glucose from carbs. This diet originally emerged as a medical therapy for epilepsy, but in the past decade it’s become a mainstream weight-loss strategy. People on keto fill their plates with foods like meat, eggs, cheese, butter, oils, and avocado, while avoiding bread, pasta, sugar, most fruits, and even starchy vegetables.

Does keto work for weight loss?

Many people do lose weight quickly on a keto diet, especially in the first few weeks. Cutting carbs causes the body to shed water weight initially and can also reduce appetite. Some research suggests keto dieters often consume fewer calories because high-fat foods and proteins are very filling. Keto’s ability to control blood sugar and insulin levels may also play a role in fat loss. However, the keto diet is far from a miracle solution. Much of the long-term weight loss success on keto depends on whether you can sustain such a restrictive eating pattern. Eliminating most carbs means saying goodbye to bread, cereals, most fruits, and even many vegetables – a difficult change to maintain for months or years.

Not surprisingly, experts caution that keto’s impressive short-term results may not translate into better long-term weight maintenance than other diets. Rankings frequently rate keto low for overall healthiness and ease, even when it ranks well for fast weight loss. The diet’s heavy emphasis on high-fat foods raises concerns about heart health if one eats too much saturated fat. Some followers experience side effects like the “keto flu” (fatigue, headache, nausea as the body adapts) or nutrient deficiencies if the diet isn’t well-planned. In short, keto can work for weight loss – sometimes dramatically – but it’s not a magic fix. It requires careful planning (favouring healthy fats and non-starchy veggies) and dedication to be safe and effective, and its long-term superiority is unproven.

The Paleo Diet: Eating Like a Caveman

Another headline-grabbing diet is the paleo diet, which urges us to eat like our Paleolithic ancestors. Also known as the “caveman diet,” paleo emphasizes whole foods that prehistoric humans might have hunted or gathered: meat, fish, eggs, vegetables, fruits, and nuts. On the flip side, paleo strictly cuts out food groups that weren’t part of early human diets – notably grains, legumes, dairy, most sugars, and anything processed.

Does the paleo approach work?

Going paleo often does lead to weight loss for many people, at least in the short run. By cutting out refined grains, sugars, and processed foods, followers naturally reduce calorie intake and tend to eat more protein and fibre, which are filling. Some studies have found that people on paleo diets lost more weight and improved certain health markers compared to those on more traditional diets. However, it’s not clear whether benefits come from “eating like a caveman” per se or simply from ditching junk food. Whole grains and legumes are nutritious staples for many long-lived cultures and provide fibre, vitamins, and minerals.

Completely avoiding entire food groups isn’t necessary for most people and could even be detrimental if it leads to nutrient gaps. Paleo diets often involve eating a lot of red meat; higher intakes of red and processed meat are linked to cardiovascular disease and some cancers. The evidence for paleo’s long-term benefits is still mixed. Emphasizing vegetables, fruits, and whole unprocessed ingredients is wise, but there’s nothing magical about excluding grains and beans if your diet is otherwise balanced.

Intermittent Fasting: Timing Your Meals

Unlike keto and paleo, which focus on what you eat, intermittent fasting (IF) is all about when you eat. Popular IF approaches include time-restricted eating (such as 16/8: fasting for 16 hours and eating within an 8-hour window) and alternate-day fasting or the 5:2 diet (severely restricting calories a couple of days per week and eating normally on others). The idea is that by prolonging the time between meals, the body will tap into fat stores and improve metabolic health. People also often naturally end up eating fewer calories, since there’s less time to eat in a day or fewer full meals in a week.

Does intermittent fasting work?

A growing body of evidence says yes – for many, it can. IF appears roughly as effective as standard daily calorie-cutting for weight loss and, for some individuals, easier to stick to. By not eating after dinner until a late breakfast or lunch the next day, you might consistently eat fewer calories without counting anything. There’s also evidence that intermittent fasting can lower insulin and ghrelin (the hunger hormone), and some studies show improvements in blood pressure and insulin sensitivity.

That said, intermittent fasting is not a magic cure-all, and it isn’t for everyone. Fasting does not give license to eat anything you want during eating periods – you still need nutritious foods and reasonable portions. Some people overeat when the fast ends, negating the calorie deficit. Others may struggle with low energy, irritability, or concentration issues when fasting, especially at first. Certain groups shouldn’t fast (e.g., pregnant women, those with a history of eating disorders, or people with specific medical conditions) unless under medical supervision. IF works best when combined with a balanced, whole-food diet.

Do They Really Work? – The Bottom Line

With all three diets – keto, paleo, and intermittent fasting – the fundamental question is: do they work, and are they worth it? In terms of pure weight loss, all three can “work” in the short term. Cutting carbs to near-zero, cutting entire food groups, or cutting mealtimes often leads to consuming fewer calories, which will make the number on the scale go down. These approaches can also kick-start motivation.

However, the bigger issue is sustainability and overall health. A diet is only as good as your ability to stick with it and how it impacts your body long-term. Restrictive diets can be hard to adhere to beyond a few months. They can also raise nutritional concerns: keto may lack fibre and micronutrients if done carelessly and can raise LDL cholesterol; paleo may fall short on calcium and fibre; IF can backfire if it triggers overeating or poor choices during eating windows. Mainstream experts still recommend proven dietary patterns like the Mediterranean diet – rich in vegetables, fruits, whole grains, lean proteins, and healthy fats – for sustainable weight management and disease prevention.

Final Thoughts

In the end, the best diet is one that you can maintain and that nourishes your body. Keto, paleo, and intermittent fasting all have success stories and some scientific support, and many people have lost weight or felt healthier adopting them. If you’re considering one of these diets, go in with eyes open: be mindful of the pros and cons, consider consulting a healthcare provider or dietitian, and keep the big picture in mind. Often, simply emphasizing whole foods and moderation – and cutting out sugary, ultra-processed foods – yields great results. There’s no one-size-fits-all answer; the real secret is finding a balanced approach you can live with for the long haul.

Sources:

• Martínez-Montoro JI, et al. BMC Medicine (2025). Randomized trial of ketogenic diet, time-restricted eating, and alternate-day fasting for weight loss.

• Harvard T.H. Chan School of Public Health. “Is the paleo diet healthy? It’s complicated.” (Updated 2024).

• Harvard T.H. Chan School of Public Health. “The health benefits of intermittent fasting.” (2025).

• Harvard Nutrition Source. “Diet Review: Ketogenic Diet for Weight Loss.”

• Paoli A, et al. Nutrients (2025). “Ketogenic Diets for Body Weight Loss: A Comparison with Other Diets.”