21 Day Fat Burning Challenge

How to run your own 21 day Fat Burning Challenge

This is my go to routine if I need to lose a few pounds quickly.

It’s a 21-Day Challenge that combines the principles from the keto diet and intermittent fasting for rapid  & safe weight loss. Works just as well for someone who needs to lose 2 pounds as someone who needs to lose 200.

Need to lose weight and don’t know where to start? Instead of doing more research, try this…

Set your 21 day goal

Mentally fill in the blank —> I want to lose _______ lbs in 21 days.

A rough estimate is fine if you have no idea. You can lose 20 pounds or more in 21 days if you follow the plan below.

My choice of 21 days is intentional. Many people sabotage themselves by setting goals too far off into the future. A 21 day deadline is tight enough to motivate you, while providing enough time to achieve substantial weight loss.

Once you hit the 21 day milestone, you can evaluate your progress and shift into maintenance phase or set another 21 day goal and keep going.

Make sure you have a bathroom scale to track your weight loss. You’ll be weighing in on day 1, day 14, and day 21.

Skip breakfast

To speed up the weight loss process, I skip breakfast and eat all my meals & snacks between noon and 8p. This is known as intermittent fasting or the 16:8 strategy (fast for 16 hours, eat all meals in an 8 hour window). You can drink water anytime. All other beverages should be consumed between noon & 8p.

If you eat or drink late night, push your lunch back the next day to offset. So if you eat a midnight snack, don’t eat lunch until 4:00p the next day and try to squeeze in your dinner before 8pm to get back on schedule.

You’ll be tempted to ignore my recommendation to skip breakfast. Marketers have successfully convinced most people that it’s the most important meal of the day. Reconsider for this 21 day experiment:

  1. You’ll lose weight faster.
  2. You’ll start to move away from mindless / unnecessary eating.
  3. You’ll be more productive.

By skipping breakfast, I’ve rewired my brain to expect food only after I’ve done the physical labor or productive work necessary to earn it. Even on days when I do an intense workout in the morning, I don’t eat til noon and I’m fine.

On leisure days, like weekends or holidays, I resist eating for as long as I can but I don’t obsess over it.

One tip to help you manage the potential social awkwardness of your new mealtimes: take the lead on proposing lunch and dinner outings. You’ll be surprised how often friends & family are totally fine with lunch at 2p or dinner at 6p. They’ll be excited that you took the initiative.

Eat meat and vegetables

This is the most impactful part of the diet. If you get this right, you win.

Carbs and sugar make me fat so I don’t eat them. Meat and veggies provide all the calories and nutrients I need so that’s what I eat. I use low carb sauces & spices to help keep the meals flavorful and indulgent so that it doesn’t get insanely boring. To kill cravings, I cook the low carb versions of my favorite foods like: Cauliflower Crust Pizza or Zucchini Pasta Alfredo.

Never had a low carb meal before? Here are some of my personal favorites:

  • Sauteed Ground Beef & Vegetables
  • Buffalo Wings with Roasted Asparagus
  • Lettuce Wrapped Italian Sandwich

If you need some recipes, I send out 1x new low carb recipe per week here:

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My favorite low carb snack foods are:

  • Pepperonis
  • Dill pickles
  • Black olives
  • Almonds
  • Pickles
  • Beef jerky
  • Dark Chocolate 85%+ cocoa (it’s allowed but I’m allergic…doh!)

I avoid bread, rice, pasta, chips, baked goods, potatoes, fruits, and all sugary treats.

Here’s my approved foods list you can reference to build your own meals.

One thing I should note. If you’re eating primarily meat & vegetables, you need to be eating a lot of fat to get enough calories. Practically, this means you shouldn’t be draining the fat off your ground meats nor should you be skimping on butters, oils, & sauces — use ALOT. I had to add this paragraph in specifically for Grandpa SkinnyPants who grew up in a generation where fat was BAD and grains were GOOD. We now know today that the exact opposite is true. Dad, if you’re reading this, don’t drain all the fat off the ground turkey!

I do meal planning and grocery shopping on weekends and try to cook something on Sunday evening so I have at least one healthy meal available to start the week.

My overarching strategy for meal prep is to keep it simple. Four times a week I’ll make something quick — like 5 ingredients sauteed in a skillet and it’s done. Occasionally, I’ll make something more time consuming like a Cauliflower Crust Pizza.

I make meals large enough to yield leftovers. When the leftovers are gone or boring me, I eat out. This happens about 5 times a week. My favorite fast food and take out options:

  • BBQ – pork ribs from Terry Black’s are my current go to.
  • Lettuce wrapped hamburger – double patties from McDonald’s or P. Terry’s.
  • Lettuce wrapped sandwich – two from Jimmy John’s for a full meal.
  • Burrito bowl on lettuce (no beans, no rice) – Chipotle w/ extra chicken and guacamole
  • Grocery store salad bars – about 1 lb of salad dressed w/ olive oil and vinegar
  • Chicken nuggets – this is a splurge, but better than most options. I get the 20-piece from Chick Fil A or McDonald’s. I sometimes share with my wife.

If you have an overwhelming craving or need a cheat day, just do the minimal amount of cheating needed to satisfy the craving, then get right back on the wagon. It won’t sink your diet as I have built in buffers to offset cheating.

Over the course of the 21 day diet, I’ll probably have 2-3 full on cheat days and another 5-10 random occasions where I eat something that’s not low carb.

Don’t drink calories

Survive on water and sparkling water. I’m a sparkling water freak. I drink as many as 5 per day. La Croix and Topo Chico are my favorite brands. You can drink unsweetened tea & coffee, but I don’t because caffeine makes me an erratic sleeper.

Don’t drink milk, soft drinks, energy drinks, smoothies or fruit juices. All are loaded with sugar & carbs. Don’t drink diet sodas either – the artificial sweeteners trick your body into thinking sugar is arriving, spike your insulin levels, and shift you from fat-burning to fat-storing.

Alcohol isn’t permitted, but you’re probably going to drink anyways (I do it too), so let’s discuss.

When I’m hardcore about losing weight, I’ll limit my alcohol intake by any means possible: arrive late to parties, skip social outings, abstain from drinks during meals, drink super slowly, etc. I am more selective about hosting parties because the leftover snacks & alcohol could linger after the crowd clears.

Tequila with sparkling water and lime is a tasty low carb drink but I’ve stopped drinking them because they cause blackouts and severe hangovers. I now drink light beer and accept the extra carbs.

Try to limit your drinking to social outings (keyword “outings” meaning don’t drink at home) and impose a 3 drink limit on yourself.

Notify your inner circle

Your family, your roommates, and your close co-workers are the people most likely to mess up your diet so alert them to your plans. You’ll know the proper tone based on the relationship, but here’s an example email script you can use:

Hey there!

I’m experimenting with a new approach to eating for the next 3 weeks. Cutting out all sugars / carbs & eating only between 1p and 8p everyday. Would really appreciate your support by not offering me any sugary or carb heavy treats for the next 21 days. It’s going to be hard enough, as is! Let me know if you’re curious about joining in and I’ll get you the details.


I work from home, so I have it pretty easy. I just let my wife know when I’m changing my diet and invite her to participate. If she opts out, I beg her not to tempt me with high carb foods (like cookies from work) and ask her to be understanding if I skip drinks or dessert when we go out to eat.

Get rid of the bad food in your home

It’s best to do this before you start your diet. Eat all the bad stuff or get rid of it. Anything that’s not on the approved foods & beverages list must go.

I hate wasting food, so I try to eat all the bad foods before I start the diet. That binge typically creates a feeling of disgust that gets me through the first few days of the diet without any cravings. If you’re not a binger, you can donate the food or throw it away.

Having roommates makes this step harder, especially if they’re not the supportive types. I figure that most won’t let you throw out all their food. Consider getting a food locker to lock up their bad foods so you can’t get to it.

Once your pantry and fridge are temptation-free, snap a few pics and tag them with #skinnypants on Instagram. You’re ready to start the 21 day diet.

Measure your progress

On Day 1 take a photo that shows your face, stomach, arms, and legs. Weigh yourself and enter the data here.

Each day, note what you ate and how you felt. Take notes on which parts of the diet come easy versus which are difficult. You’ll use this information later.

Weigh yourself again on Day 14. I recommend waiting 2 weeks for your first weigh-in because it’s easier on the psyche. Some people weigh themselves everyday and it causes frustration because weight loss isn’t linear. You can go 5 days without losing weight and then lose 5 pounds in a day — this is called whooshing.

On Day 21, do your final weigh-in and retake the photo you took on Day 1. Review your progress pic and answer the following questions for yourself:

  • How much weight did you lose?
  • Can you see a difference?
  • How do you feel mentally & physically?
  • How many more 21 day diets would it take to reach your ideal weight?
  • Are there components of this diet that you can adopt for the long term?

For me personally, the results of this diet were powerful enough for me to adopt it as my everyday eating plan.

Closing thoughts

The extremes of this diet won’t be necessary once you reach your ideal weight. It’s intentionally aggressive to make certain you’ll lose weight. The closer you come to matching my recommendations, the more weight you’ll lose, but you don’t have to be perfect to lose weight. The key steps are:

  • Skip breakfast
  • Eat meat & veggies
  • Don’t drink calories

Take note of the things that are easiest for you to implement as those habits will be part of your long term maintenance plan once you hit your ideal weight.

Need some motivation?

If you want some motivation and would benefit from seeing others who have gone through this process?

Check out others just like you who have all lost weight with this “Mr Skinny Pants Approved’ approach!

Need some help?

We work with people who have “tried every diet” and still have not achieved results. If you want a personalized, proven method using a keto or low carb approach, let’s chat! Cheers, Mr. Skinny Pants

How to lose 30 pounds on keto

12 thoughts on “21 Day Fat Burning Challenge”

    • Baby SkinnyPants gets his breakfast. Usually a banana and 4-5 all natural sausage patties + some random veggies. I think kids need morning calories because they are growing and expending more energy than most adults. Plus, they cry more when hungry which is annoying :).

      • Agreed! Just curious what Baby SkinnyPants was doing when you & the wifey were starving! Our SugarBabies eat sausage/bacon and eggs for breakfast most days, unless SugarDaddy (named for copias amounts of sugar intake – not for his cash on hand) has a donut craving. I’m going to jump on and try this…but it may be next week before I start. Gotta clean out the old pantry and fridge.

      • Agreed. Many claim you should subtract your sugar alcohol grams from Carbs to calculate Net Carbs, but I tried this and it brought my weight loss to a screeching halt. For me, they’re a NO-GO.

        Quest bars are far too sickly sweet for me. I wish they were 1/4 to 1/2 as sweet as they are.

  1. Can you help a chic who works 7pm to 7am and lunch is scheduled between 11pm and 2 am? All the formats and templates are for people who works normal daytime hours..

    • Yep! There is no ‘magic formula’ so you can adapt hours to fit your schedule. We are all different so what I laid out here might actually not be perfect for you specifically (schedule aside) You can try smaller snacks throughout the day (if that’s allowed at work) You can try to schedule your fasting period around your work day (it doesn’t have to be in the morning) Keep tinkering till you find a groove that you can stick to and one that produces results! 🙂

  2. Is counting Net Carbs a better approach than just counting regular carbs? I have read a lot of differing opinions.
    Thank you.

  3. I’ve done keto a few years back. Lost 100lbz. I know it it works..everything about myself felt better..inside and out..now that ive gained it all back.. im having trouble getting dedicated to it again..that kind of failure rides hard on the physique…help..


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