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Rapid Fat Loss for Vacation


What would be the best way to lose fat quick as I am going on vacation in 4 weeks. Because of my work schedule I can only get in the gym 3 days a week. What’s the best approach? Drop calories and hit cardio hard? Or would that set my metabolism up for a crash later? I am about 230 lbs and want to drop at least 15. Would a Keto type diet be best. Or would it be best to keep some carbs in for training purposes. Thanks


This was the very subject of a recent TNation roundtable, which included CT, where experts gave their advice on rapid fat loss. Hopefully you can inject a bit more energy into your own efforts to reach your fat loss goals, though I doubt it when you can’t even be arsed doing some simple research on this site.


Dropping calories very low for 3-4 weeks should not set you up to crash. And while you are on vacation cortisol will go down which should actually help you improve your metabolism. The main issue might come from eating and drinking like a pig while on vacation.

This is from an article on my website:


This is an approach where you basically do everything possible to lose fat as fast as possible. It’s an extremist approach. Everything is pushed to the limit right out of the gates. It is not something that is sustainable for long, or even for a moderate time. Well, it is if you have an iron-clad discipline and don’t care about health, well-being, performance and muscle mass.

Caloric intake

You start off with an extreme caloric deficit. How low do you go? This will depend on the individual of course, but if we use the work of Lyle McDonald as a reference (Ultimate Diet 2.0), you would cut your maintenance calories by 50% without going lower than 1200 calories for men and 900 calories for women. Even though we had our differences, I must say that Lyle is one of the smartest individuals in the world when it comes to diet.

So, if your maintenance calorie level is 2800 kcals per day, your daily intake would be 1400 kcals.

What is your maintenance calorie level? It depends on the individual and their activity levels. For most people, it falls between 14 and 17 calories per pound of body weight, but there will be some variation. For example, someone who is 350 lbs with 40% body fat would have a theoretical maintenance level of 4900 – 5900. This is likely too high, but it can give you a good starting point.

The method I prefer is to write down everything you eat/drink for a week (including quantities), calculate your average daily caloric intake and register the difference in body weight between day 1 and day 7. If your body weight didn’t change, you likely ate at around maintenance level, if weight went up, your average intake was a surplus and if it went down, it was a deficit. So, it can help you get a pretty good idea of where your maintenance level is.

Protein needs to be high to prevent muscle loss. 1.25g per pound of body weight is a good starting point. This will not leave much room for carbs and fats: if you are 200lbs, it represents a protein intake of 250g which is 1000 kcals from protein. If your blitz caloric intake is 1400 kcals per day, that leaves you with only 400 calories from fat and carbs combined. You can use any fat/carbs combo as long as you stay at your calculated level.

400 kcals from carbs and protein could be:

– 0g of carbs (0 kcals) and 44g of fat (400 kcals)

– 25g of carbs (100 kcals) and 33g of fat (300 kcals)

– 50g of carbs (200 kcals) and 22g of fat (200 kcals)

– 75g of carbs (300 kcals) and 11g of fat (100 kcals)

I would personally go with the first or second option but it depends on each person.

Weight training

I don’t like to use the lifting session as a fat loss tool (although it will help). I prefer to design the sessions to maximize muscle mass retention. Normally when volume is too high, cortisol is increased which increases the chances of losing muscle. BUT this is a blitz: you want the fastest fat loss possible. You are not likely to lose muscle mass in 4 weeks even if the volume is high and cortisol release is increased. Chronic cortisol increase is a problem, but as part of a blitz it is probably okay.

So, I would increase training volume versus what you normally do, maybe doing 25-50% more volume. I would also shorten the rest intervals to keep energy expenditure higher. So basically, your training time will be the same, but you will be doing more work with less rest.

If it is something your schedule allows you to do, you could train twice a day. In that case I recommend training the same muscle(s) in both sessions of the same day. You would go heavier in the first session and for more of a “pump” in the second.

Cardio/Energy systems work

You would start right off the bat with a high amount of cardio work. This means a high frequency: 5-6 days a week.

The type of cardio you select will depend on your neurotype, the key is just doing it. Read this article for some options for your type: https://thibarmy.com/the-best-fat-loss-tools-for-your-neurotype/

I prefer to do the cardio as a separate session in the day, but if you can’t, do the cardio after your lifting.

Since this is a blitz you start immediatly with a high amount per session (see the article linked above for recommendations) because you won’t increase it during the 4 or so weeks of the blitz.

Pros and Cons of the blitz approach


– It’s over quickly. Few people like the dieting down process since it’s all about discipline and restriction. Some do better on it than others, but for a lot of people it’s hell, and they prefer to suffer a bit more but be over with it sooner than later.

– If you are a very intense/excessive person, it will fit your personality better. Some people don’t get motivated unless they feel like they are doing everything possible to reach their goal. Not only that, they need to do everything at the extreme level.

– It gives rapid significant results. While it may displease the “don’t lose more than 2 lbs per week” crowd, cutting calories to a greater degree and exercising more will give faster results than a more conservative approach. And no, at first, it should not lead to muscle loss since you are doing this for a brief period only and losing muscle is about the third strategy the body will use to cope with caloric restriction.

– Mentally, I find that it puts you in the zone more easily. It makes the process more real because it is such a drastic departure from your normal habits. Being in the zone can make it easier to stay focused and stay the course.


– For some people (some neurotypes) there is a chance of losing muscle. This is the case of those who naturally overproduce cortisol (Type 3 and Type 2B). Cortisol is one of the hormones responsible for mobilizing stored nutrients for energy when your diet doesn’t provide enough and to increase blood sugar levels when it is too low: two things that will happen when you diet (especially with the blitz approach). Some people are better at doing that mobilization via growth hormone or glucagon, so they are less likely to lose muscle. But if you naturally overproduce cortisol the chances of losing muscle on a blitz diet is real.

– You will have energy crashes and likely will feel like crap from time to time. While this is true for all fat loss diets (to some extent), it is much worse with a blitz approach. After all, the energy deprivation is much greater and energetic nutrients are super low. Sure, you will mobilize body fat for fuel and you can also rely on some ketones, but these are not as efficient as carbs when it comes to fueling intense workout or the brain. Even those who are pro-keto admit that the first 2-3 weeks might be hard on energy and mental focus until the body adapts to ketones. Well, with a blitz approach you don’t really reach that adaptation state.

– Your workouts will start to suck. The first week you will be fine: you will be running on the stored glycogen from the pre-diet time. After that you will see a drastic decrease in training energy: you will lose some strength and some resistance, this will be made worse by the higher training volume and cardio. You will have less energy and drive to train. This is where a lot of people compensate by using high doses of stimulants, an approach I’m not comfortable recommending for several health reasons. The low level of glycogen and problems staying hydrated due to the low carbs will also make it much harder to get a good pump, which can be mentally hard.

– You will feel flat like a pancake. As I just mentioned, your glycogen stores will be close to empty. That means that your muscles will feel smaller, softer and flatter. This can be demoralizing because it will also make you look much worse while you are trying to look much better! But it’s not muscle loss, it’s only your muscles being “deflated”. Even if you know and accept that, it is still very difficult psychologically and can make it harder to stick with the process.

– If done for too long, the blitz approach can also lead to some problems like “metabolic damage”… really, all that is is a decrease in the active thyroid hormone (T3). T3 is one of the main hormones that determines how high your metabolic rate is (how much calories you burn per day even at rest). If T3 goes down, your metabolic rate goes down and your caloric expenditure also goes down. The body doesn’t produce much T3 directly. It produces T4 (which is mostly inactive) and converts it into T3 as needed. Chronically elevated cortisol (which happens with any dieting but is greater with larger deficits) and carbohydrate deprivation will drastically decrease that conversion, leading to a lower T3 level. That’s what metabolic damage is.

My interpretation

The blitz works best in 3 situations:

– If you are already lean and want to drop the last few pounds of stubborn fat to get shredded.

– If you are obese and need to drop a lot of fat in a very short period of time (e.g. before a bariatric surgery).

– If you want to rapidly drop a good amount of fat in a short time for a special occasion (e.g. beach vacation).

The biggest potential problem is using a blitz approach to get shredded or super lean but underestimating how much fat you have to lose to look awesome. For example, Mark thinks he only needs to lose 15lbs to be ripped. He goes on a 5 weeks blitz and at the end he has lost 17lbs but is not yet shredded.

Here’s the problem: Mark still has fat to lose to reach his goal after 5 weeks of all-out dieting/training. The thing is that if he continues with the same restrictive approach, he is likely to cause issues that will negatively affect his physique (loss of muscle, decrease in metabolic rate, decreased fat loss) and potentially health. BUT if he switches to a moderate dieting approach he might not continue to lose fat because now his body adapted to the super low calories/high activity levels. That’s the danger of the blitz: if you have not reached your goal within 4-5 weeks, you are in “trouble”. That’s why it works best when the goal is not necessarily reaching a certain “look” but losing a lot of fat in a specific time frame.

As for the neurotype, the blitz approach works best for Neurotypes 1A and 1B . These guys are results driven (they need to see a lot of results fast). They also produce less cortisol, so they won’t risk losing muscle in the short period of the blitz. They are also “intense” personalities that do better when they go all-out.

Finally, they are more negatively impacted then others by a decrease in leptin levels. Leptin levels will drop when you get leaner and are in a caloric deficit for a while. The longer your diet down, the more leptin will drop. Since 1A and 1B are more affected by leptin, they do better on short dieting phases.

The fat loss blitz is the worst approach for Type 3 individuals as they are cortisol overproducers and have a low level of serotonin (which will get even lower when cutting carbs and calories drastically). These guys will become more anxious, won’t sleep well, can lose muscle and will have huge mood swings when using such an approach.