Keto Diet for Weight Loss: Is Low-Carb Really the Best for Burning Fat?

by Elliot Reimers, M.S.(C), CISSN, CNC | Reviewed by Advisory Board

Keto Diet for Weight Loss: Is Low-Carb Really the Best for Burning Fat?

Is Keto Really the Best Diet for Weight Loss?

A ketogenic diet, or simply "keto," is undoubtedly the most popular weight-loss diet of the 21st century. Consequently, many people get wrapped up in all the ballyhoo and what periodicals have to say about keto for weight loss. Odds are, masses of "carbophobes" have convinced you keto is nothing short of a miracle diet for getting rid of stubborn body fat while gorging on bun-less bacon cheeseburgers.

Yet, research on very-low-carb, high-fat diets like keto doesn't seem to justify much of the buzz [1]. Sure, there are studies that support the merits of a keto diet for weight loss and possibly treating specific diseases, but this seems to be another case of anecdotal hype outpacing the empirical data — an all-too-common phenomenon in modern health and fitness subculture.

Before you jump on the low-carb bandwagon in hopes of burning fat and losing weight, it's crucial to weigh the pros and cons of such a drastic lifestyle change. On that note, this article will expand on what keto is and five key things you should consider about using a very-low-carb diet for weight loss.

What is a Keto Diet?

keto diet weight loss

On the off chance you're not familiar with a ketogenic diet, don't worry — it's pretty straightforward. In short, a keto diet is a very-low-carb, high-fat diet that encourages the body to produce more ketone bodies, namely acetoacetate, acetone, and beta-hydroxybutyrate (BHB). As ketone body production increases, the body transitions to a physiological state of nutritional ketosis (not to be confused with the medical condition diabetic ketoacidosis).

When you're in ketosis, the body relies less on blood glucose for energy and more on fat and ketones. In fact, ketones are a byproduct of fat oxidation (burning) in the liver. Hence, a keto diet encourages a much higher fat intake than a conventional low-fat, higher-carb diet. Some keto advocates will use the term "fat-adapted" to describe ketosis, but this is a bit of a misnomer given that the human body is intrinsically adapted to use fat as a source of long-term energy even on higher-carb diets.

The catch is that carb intake needs to be stringently restricted, typically less than 30 grams of net carbs per day. Eating too many carbs will limit ketone production and kick you out of ketosis since the body will revert to using blood glucose for energy. In reality, your body will still use some blood glucose for energy regardless of how few net carbs you eat, just not as much as it normally would.

How Much Should You Eat to Lose Weight on Keto?

A standard ketogenic diet is what most people follow to lose weight.The typical macro breakdown (as percentage of calorie intake) for a standard keto diet is:

  • 75% fat
  • 20-25% protein
  • ≤5% carbs

These macros are a good starting point for individuals that are ready to commit to a low-carb lifestyle. This means you will need to eschew starchy and sugary foods, as well as monitor carbohydrate intake diligently.

Is a Keto Diet Good For Weight Loss?

There's no shortage of anecdotes and personal success stories on the Internet about using keto for weight loss, so it absolutely does work for some people. But there is no cookie-cutter "best diet" to lose weight. Even for those who follow keto, the same overarching principle dictates weight loss: calories in vs. calories out (i.e. energy balance).

Energy balance is the most influential factor in improving body composition (e.g. burning fat and building muscle). If you eat too many calories, you won't be burn body fat; it's that simple. This seems to be where many keto zealots get confused since they think cutting carbs means the body is "forced" to burn fat for energy around the clock. Well, yes, but not exclusively body fat. You eat more fat on a keto diet, so you burn more dietary fat for energy. And lest we forget, fat is the most calorie-dense macronutrient, making it easier to overshoot your energy balance if you're not careful.

keto diet energy balance

Nevertheless, there's good evidence that keto can help people who want to lose weight, especially those who struggle with sugar cravings/appetite control and live a sedentary lifestyle [2]. A handful of studies also suggest that a very-low-carb diet may be prudent for controlling insulin levels in overweight/obese diabetics [3].

But does that mean a keto diet is "best" for weight loss? Not by a long shot. Keto can work wonders for some and do the opposite for others. And for those who do lose weight on keto, one could argue that it's not necessarily the ideal approach. Many diets "work" to an extent, but that doesn't make them optimal.

Heck, a vegan diet has countless health benefits, but that's no reason to claim it's unequivocally the best way for humans to eat. Nutrition is relative to your goals and specific needs.

5 Reasons a Ketogenic Diet May not Be Best for You

Before you clear out all the carb-laden foods in your kitchen cupboards and fridge, there are some finer points to consider about why keto may not be all that great for weight loss.

A Keto Diet May Not Be Sustainable in the Long-Term

The salient counterargument to those considering a keto diet for weight loss is its potential impracticality as a long-term lifestyle. Be honest with yourself: Do you really think you want to eschew carbohydrates for the foreseeable future? How will it impact your social life? Are you going to feel the need to "cheat" on your diet when dining out with friends and family? These are all questions you need to contemplate before starting a keto diet.

It's one thing to lose weight, but none of it matters if you regain it shortly after reaching your goal. There is no reason you can't get lean while eating a modest amount of carbs, and research suggests that a "flexible diet" leads to better long-term success and adherence than restrictive diets like keto [4, 5].

Are Ketones Really a Good Source of Energy?

“Fitness gurus” will often contend that low-intensity, steady-state (LISS) cardio paired with keto or fasting is best for fat loss since muscles rely mainly on fatty acids and ketones for energy at lower intensities. The problem is that LISS cardio in and of itself is mostly just a way to burn calories (and train the cardiovascular system); it doesn’t do much beyond that.

On the contrary, high-intensity exercise, like sprinting and weight lifting, relies on anaerobic glycolysis and the phosphocreatine system for energy. Thus, athletes and gym-goers that train at higher intensity may fatigue quickly and lose strength on a hypocaloric keto diet. There is limited evidence that exogenous ketone supplements may serve as a viable energy source for exercise, but nowhere near the amount of data backing the ergogenic effects of carbohydrate supplements [6, 7].

Carbs Preserve Lean Body Mass on a Weight-Loss Diet

Tl Carb powder

Most people who begin a ketogenic diet are under the impression that rapid weight loss is best. Sure, it's a psychological boon when you see the number on the bathroom scale drop during the first week of a diet that's very low in carbs, but most of that is merely water weight. Remember that weight loss is not the same as fat loss; the two are vastly different in terms of health and longevity. 

When your body is severely deprived of energy (calories) and carbohydrates, it resorts to breaking down both fat and, if necessary, lean muscle tissue to generate fuel. Glucose is a protein-sparing nutrient, and insulin is one of the most potent anabolic and anti-catabolic hormones in the body [8, 9]. Carbohydrates are essentially synergistic with protein for protecting and building skeletal muscle. When you remove them from the equation, the synergy is lost.

So, if you're goal is to get to a low body-fat percentage while maintaining as much lean body mass as possible, a keto diet is unlikely to accomplish that. The smarter strategy would be a carb-cycling diet with methodical high-carb refeed days.

Keto and Athletic Performance

Since glucose and glycogen are hydrophilic ("water-loving") molecules, it’s not unusual to experience bloating after eating a starchy meal and drinking large amounts of water to wash it down. On the contrary, the keto diet acts as a natural diuretic, causing people to lose water weight as glycogen stores are depleted and carbs are eliminated from the diet.

While that may be desirable in the short-term, dehydration and electrolyte imbalances may lead to flu-like symptoms (aka "keto flu") such as cramping, headaches, and constipation. Consequently, this can hinder athletic performance.

If you do end up using keto for weight loss, make sure you drink plenty of fluids (preferably purified water) and replenish electrolytes by using a supplement, such as Transparent Labs Hydrate. In addition, eat plenty of low-carb, mineral-rich foods.

Here are some of the best keto-friendly dietary sources of magnesium and potassium: 

  • Spinach
  • Broccoli
  • Cucumbers
  • Collard Greens
  • Avocados
  • Almonds
  • Salmon

Keep in mind that caffeine/stimulants are diuretics, so if you drink a lot of coffee while following a very-low-carb diet, you will need to compensate by drinking more fluids. A fool-proof way to assess your hydration status is monitoring the color of your urine — if it's clear, you’re good to go; if it's dark yellow (or orange), you're dehydrated!

A High-Protein Keto Diet May Reduce Kidney Function

It is well-established that people with chronic kidney disease or other renal dysfunctions need to avoid a high-protein diet, but what about those with healthy kidneys? There's a longstanding notion (largely a myth) that high-protein diets are bad for the kidneys. Naturally, this might lead people to believe that a keto diet is bad for the kidneys since it generally includes more protein than a typical diet.

However, protein intake may not be the issue. Research has shown that certain protein sources have a significantly lower impact on glomerular filtration rate (GFR) — a biomarker of kidney function — than others [9, 10]. Beef, pork, poultry, and fish tend to increase GFR to a greater extent than egg whites, dairy proteins (i.e. casein and whey), and plant-based proteins (e.g. soy, pea, and rice). Essentially, an acute spike in GFR after a meal means the kidneys are working "harder" to filter waste in the blood. Over time, this can damage nephrons in the kidneys.

Interestingly, even though eggs and dairy are sources of animal proteins, they elicit a rise in GFR commensurate to plant proteins. As such, using a protein powder that contains egg whites, whey protein, and/or casein protein is generally safe for the kidneys. 

TL Grass-fed Whey Protein

Furthermore, plant proteins have actually been shown to protect the kidneys [11]. It's pretty clear that eating more plant-based protein and less red meat, pork, fish, and poultry as part of a high-protein diet will better preserve kidney function in the long run.

But like anything, moderation is key. Eating a steak now and then won't harm the kidneys. Alas, those who follow keto tend to use it as a free pass to eat lettuce-wrapped bacon cheeseburgers and chicken wings five times a day.

"How much weight can I expect to lose on keto?"

If you do decide to go the keto route, a realistic (sustainable) rate of weight loss for active individuals is 1-2 pounds per week. As a friendly reminder, losing weight on keto is not a quick-fix. No matter what diet you follow, give yourself more than enough time to reach your goal body weight. Burning fat takes time, so don't be discouraged if you're "only" losing 1 pound per week. Consistency is the name of the game; small progress on a weekly basis will amount to significant changes if you stick to the plan!




Elliot Reimers, M.S.(C), CISSN, CNC
Elliot Reimers, M.S.(C), CISSN, CNC

Author

Elliot holds a B.S. in Biological Sciences from the University of Minnesota, as well as being a Certified Sports Nutritionist (CISSN) and Certified Nutrition Coach (CNC). He is currently pursuing a Master's of Science in Molecular Pharmacology and Toxicology at Michigan State University. Elliot began freelance writing circa 2012 and has since written 100s of articles and several eBooks pertaining to nutritional science, dietary supplements, exercise physiology, and health/wellness. Being a “science whiz,” he has a passion for helping people understand how nutrients (and other chemicals) and exercise work on a cellular and molecular level so they can make smarter choices about what they put in, and do with, their bodies. When Elliot is not busy writing or studying, you can find him pumping iron, hiking the mountains of beautiful Colorado, or perusing nutraceutical research.



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