Can eating fat help you lose weight?
Fat makes your meals more palatable and helps you feel full, so it’s no wonder the high-fat ketogenic diet is increasing in popularity. The diet has been trending for the past three years, as “keto” blogs and cookbooks continue to pop up and build an impressive fan base. This diet has been used under close supervision by physicians and dietitians since the 1920s for treating epilepsy and has shown promise in managing brain cancer. But is it useful and healthy as a strategy for weight loss?
First, the basics: On the ketogenic diet, at least 70 per cent of your daily kilojoules come from fat. Five to 10 per cent of your kilojoules come from carbohydrates (20 to 50 grams a day). The rest, up to 25 per cent of your daily energy, comes from protein. By contrast, the healthy diet recommended by the Institute of Medicine is 45 to 65 per cent carbs, 20 to 35 per cent fat and 10 to 35 per cent protein.
The ketogenic diet’s low-carb target can be met only by avoiding grains, dairy products, fruit, and legumes such as chickpeas and lentils. Starchy vegetables such as sweet potatoes and squash are out, and even amounts of lower-carb vegetables are limited.
So what’s left to eat? Typically, eggs cooked in butter for breakfast; for lunch and dinner, meat, chicken or fish with salad or green vegetables and plenty of oily dressing. Sorry folks, no alcohol on this diet. Even red wine is out.
The ketogenic diet gets its name from a process called ketosis. Ketosis happens when your body doesn’t have enough energy from glucose (carbohydrates), so it adapts by using stored fat for energy. The result? Weight loss.
Does the ketogenic diet lead to faster or more sustainable weight loss than other diets? The research to date suggests that initial weight loss on the keto diet is impressive but that people aren’t able to stick to the regime for long.
One study, for example, compared the impact of a ketogenic diet (where participants ate less than 20 grams of carbohydrates a day) to a low-glycemic-index diet (where participants reduced their caloric intake by 500 a day) on weight loss in 49 obese individuals with Type 2 diabetes. After six months, the group on the keto diet lost an average of 11.3 kilograms, while the low-glycemic-index group lost 6.8 kilograms.
But a recent meta-analysis combining the results of 13 randomised-control trials (1,415 participants) of a year or longer found that people on a ketogenic diet lost an average of one kilogram more after a year and improved their triglycerides, high-density lipoprotein (HDL) cholesterol and blood pressure compared to those on a low-fat diet. However, when the researchers looked at studies that followed participants for two years, they found that HDL improved more in the keto diet group but that there was no difference in weight loss between the groups.
While the ketogenic diet is promoted as key to switching your body into fat-burning mode, research suggests that fat loss actually slows down as your body starts to break down your muscle for energy.
Pros of the ketogenic diet
1. You don’t need to count kilojoules
Instead of worrying about kilojoules and portion sizes, some people find it easier to have a list of foods they can eat as much as they want of. By limiting the foods you can choose, this diet limits your caloric intake without you having to think about it too much. You might start out overdoing the bacon and pork rinds, but that won’t last. (See No. 2.)
2. You won’t be hungry
Research on the ketogenic diet suggests that the production of ketone bodies lowers your levels of ghrelin, a hormone that makes you hungry. Essentially, you’re able to stay satisfied for longer on this diet.
3. Fast weight loss (at first)
When you limit carbohydrates in your diet, your body uses the carbohydrate stored in your muscles and liver (called glycogen). Glycogen is stored with water, so restricting carbs famously helps you lose weight quickly by causing you to lose water weight. Although it doesn’t make you lose “real” weight (i.e. fat) or make you any healthier, this early perceived weight loss can help motivate people to continue with the diet.
4. There are potential heart health benefits
The majority of studies and systematic reviews on the ketogenic diet have found that following it for anywhere from three months to three years significantly improves levels of triglycerides and HDL cholesterol and increases the size of low-density lipoprotein (LDL) cholesterol particles, lowering the risk of heart disease. Studies also have shown the keto diet reduces blood sugar, insulin, C-reactive protein (a marker of inflammation) and waist circumference.
While these results seem impressive, remember that any weight-loss diet will result in improvements in these sorts of metabolic risk factors.
Cons of the ketogenic diet
1. It’s boring
The worst part of the ketogenic diet is that it’s very limited and can lead to taste fatigue. Eat the same things over and over, and eventually you’ll crack and want something off the menu.
2. There goes your social life
Socialising while on this diet is a challenge, which is another trade-off most people aren’t willing to make. Alcohol isn’t allowed, and having a bite of dessert isn’t, either. Can you be sure the salad dressing you order on the side doesn’t have sugar or honey in it? I’ve had clients tell me after trying this diet that they have turned down plenty of social gatherings to avoid temptation. That doesn’t seem like a healthy lifestyle change to me.
3. Digestive woes
As with other low-carbohydrate diets, getting enough fibre is difficult on the ketogenic diet. The result? Constipation in the short term and, over time, an increased risk of colorectal cancer. Any diet that throws off your digestive health should raise red flags.
4. Risk of nutrient deficiencies
Because the ketogenic diet cuts out so many foods, it can be deficient in the nutrients those foods contain — calcium, magnesium, selenium, thiamine, vitamin D and vitamin C. Before trying it, be sure to consult with a registered dietitian to ensure that you’re meeting your nutrient needs, especially if you’re planning to follow this diet for more than a couple of weeks.
5. There are general safety concerns
Consider that people who go on the keto diet for epilepsy are very closely monitored by a medical team, so this isn’t a diet to be taken lightly or to do on your own. Anyone with health problems should speak to a physician before trying the ketogenic diet. Don’t try it if you have kidney problems, as it hasn’t been studied in people with impaired kidney function. This diet is not safe for pregnant or breast-feeding women.
The bottom line
As researchers have stated, the benefits of the ketogenic diet are of little clinical significance — that is, any advantages over other diets are too small to make a difference in your life. Consider how following such a restrictive diet will affect your quality of life and enjoyment of food.
People who feel more energised on lower-carb diets and enjoy eating fats and oils could do well on the ketogenic diet. Anyone like me who loves their fruits, whole grains and vegetables will struggle to avoid their favourite foods. Are you willing to give up that piece of dark chocolate or Greek yoghurt with berries?
In the end, the best diet isn’t really a diet at all. It’s a way of eating you can stick to that will boost your overall health – and won’t leave you feeling zapped or require you to be antisocial.
The Washington Post
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