The Best Ways to Lose Weight, According to Science

If you’ve ever tried to lose weight, then you know that the dieting advice out there can be overwhelming — and often conflicting. Do a 5-day juice fast! Eat only meat! Go ultra low-fat! The problem is, many diets aren’t backed by good science, and you’re left feeling hungry, irritable, and unsatisfied. Even if you do lose weight, sticking to such extremes isn’t sustainable, and you end up right where you started — or worse, heavier than before. But it turns out there are healthy ways to lose weight and keep it off — methods backed by solid research. Read on to discover the best science-backed diet tips to losing weight.

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How to lose weight fast

Sometimes you just want to fit into those skinny jeans, and you want to do it now. That’s where the Bulletproof Rapid Fat Loss Protocol comes in. It helps you lose weight, and fast. You only want to try this method if you’re significantly overweight or obese, and you have healthy, functioning kidneys and liver. Otherwise, following the Bulletproof Diet, combined with intermittent fasting, is a safer and more sustainable solution for weight loss (more on that below).

The Bulletproof Rapid Fat Loss Protocol puts you into ketosis — when your body burns fat for energy — for 6 days, followed by 1 day of carbo-loading combined with supplements to help your body get rid of toxins released from your fat.

If this sounds like the best weight loss plan for you, get started with the Bulletproof Rapid Fat Loss Protocol here.

How to lose weight and burn fat: a more sustainable approach

While the rapid fat loss protocol is great if you’re looking to lose weight very quickly, it’s a better idea to find a sustainable eating plan that you can easily follow in the long-term. Follow these 5 weight loss tips to reach your body goals:

1. Follow a high-fat, low-carbohydrate diet

If you’ve ever “gone on a diet,” it’s probably been some version of the decades-old low-fat, high-carb regimen. You probably know that the diet didn’t work — it left you with sugar spikes, energy crashes, cravings, and ultimately no weight loss.

New research is debunking earlier claims that fat is bad.^[1] It might sound counterintuitive, but you need fat to keep the fat off.

There’s science to it: When you load up on the right kinds of fat and limit carbs, you force your body to burn fat rather than glucose (aka sugar) for fuel. This puts you into ketosis — when your liver converts fatty acids into molecules called ketones to use as energy. That’s why the trendy high-fat, low-carb keto diet is so popular — it turns your body into a fat-burning machine.^[2] 

Related: Ketosis and the Ketogenic Diet Explained — A Complete Beginners’ Guide

Ketones suppress ghrelin (your hunger hormone), and increase cholecystokinin (CCK) — the hormone that keeps you feeling full.^[3] You naturally end up eating less as a result — when you’re not hungry, it’s easier to go for longer periods without food. This forces your body to tap its fat stores for energy.

Eating fat gives you another metabolic advantage: it doesn’t trigger the release of insulin the way that glucose does. Insulin tells your cells to store fat, and the more insulin your body produces, the more fat that gets stored.^[4][5]

So how do you lose weight on keto?

On a keto diet, you want to eat mostly fats (75% of your daily calories), some protein (20%), and a very small amount of carbs (less than 5 percent). Keto diets like Bulletproof focus on grass-fed meat and butter, wild fish, organic vegetables, and healthy fats like avocado and coconut oil. That way, you stay healthy while losing weight. Eating unhealthy fats, such as on a dirty keto or Atkins diet, ramps up inflammation, which makes weight loss more difficult.^[6] Take a look at the Bulletproof Diet Roadmap to make sure your keto diet is also Bulletproof-approved.

2. Choose a cyclical keto diet

Restricting carbs for a long time can cause problems in some people, like thyroid issues, fatigue, dry eyes, and insomnia.^[7] Your body needs some carbs to perform at its best. That’s why Bulletproof recommends a cyclical keto diet — when you go in and out of ketosis on a weekly basis. On cyclical keto (aka carb cycling), you eat more carbs on one day of the week — roughly 150 grams of carbs. On the other 6 days you follow the standard keto diet, and eat less than 50 grams of net carbs a day.

Related: How to Start Keto & Why Cyclical Ketosis Is Better

Here are some of the benefits of carb cycling:

• Keeps you slender
• Satisfies carb cravings
• Stronger immunity
• Better sleep
• Balances gut bacteria

So go ahead and eat clean carbs like sweet potatoes, squash, and white rice one day a week. Doing this will keep your body systems that need some amount of carbs working properly, and it’ll keep the weight off for the long haul.

3. Don’t cut calories

Restricting calories is another outdated recommendation that can actually cause you to put on weight.

When you cut calories, you signal to your body that food is scarce — this puts you into famine mode. Your metabolism slows down to preserve the calories you’re taking in, and this slower metabolism can remain even after you’ve stopped restricting calories.^{[8] [9]} Eating fewer calories can also cause:

• Tiredness
• Irritability
• Nutrient deficiencies
• Constipation
• Short attention span
• Hunger and cravings
• Headaches
• Anxiety

Cutting calories can be especially hard on women. As a woman, you evolved to remain fertile and reproduce, but when you restrict calories and healthy fats, your body thinks that there isn’t enough food to make a baby. Your fertility will stop until you get more calories in to support reproduction.^[10] 

So how do you lose weight without restricting calories? You fast. Science shows you can lose a lot of weight with intermittent fasting.^{[11] [12]} Read on to find out what it is, and how it can help you drop weight, and quickly.

4. Do intermittent fasting

Intermittent fasting simply means you eat all the food you need during a shorter window of time. There are various methods, but the most common involves eating over a 6- to 8-hour window and fasting for the remaining 14 to 16 hours. With Bulletproof Intermittent Fasting, you skip breakfast and replace it with buttery Bulletproof Coffee to keep hunger levels in check (more on that later).

Fasting for short periods of time is actually the natural state for your body to be in. Your ancestors evolved in situations where food was scarce, and their bodies learned to thrive while fasting.^[13] Intermittent fasting carries all kinds of mental and physical benefits, including accelerating weight loss. Fasting gets you into ketosis quicker — it drains your glucose reserves, forcing your body to reach into its fat stores for energy.

In one study, mice who ate within a 9- to 12-hour period put on less weight and had lower fat mass than mice who ate at all hours.^[14] Another study found that obese people who ate 25% of their daily calories on one day, then ate normally the following day (aka alternate day fasting method), lost up to 13 pounds over an 8-week period.^[15] 

How to intermittent fast

When you’re following the Bulletproof Diet, you skip breakfast, and eat lunch and dinner within a 6-hour window — that gives you an 18-hour fast. Most people can fast everyday, although women sometimes need to fast every other day or a couple of times a week. You can learn more here about how to intermittent fast if you’re a woman. Experiment to see what works for you.

Check out a sample Bulletproof intermittent fasting schedule here.

Skipping breakfast isn’t easy — distracting hunger pangs, anyone? But there’s a hack to keeping the “hangries” at bay.

5. Drink a Bulletproof Coffee in the morning

Drinking a Bulletproof Coffee instead of breakfast sends a signal to your body that you’ve eaten, and you won’t feel hungry. Each cup contains black coffee, grass-fed butter, and Brain Octane Oil — a purified form of saturated fatty acids called medium-chain triglycerides (MCTs), sourced from 100% coconut oil. By eating fat only — no protein or carbs — you remain in fat-burning ketosis. The high dose of high quality fats keeps you full for hours, so you can power through your morning without dreaming of bagels.

You can get the official Bulletproof Coffee recipe here.

Brain Octane also raises your level of ketones — four times more effectively than regular coconut oil.^[16] Use Brain Octane in your coffee and drizzle it over your meals — it creates a background level of ketones by keeping ketones up to 0.7 (that’s millimoles per liter). A blood ketone level of 0.5 is enough to suppress appetite.^[17]