Curtis G. Northcutt

cgn |AT| mit |DOT| edu

Photo of Curtis G. Northcutt, Ph.D. Candidate at MIT.

CEO & Co-Founder of Cleanlab. I enjoy building AI companies to empower people. My scientific contributions focus on theory and algorithms for artificial intelligence including dataset uncertainty estimation and augmenting human capabilities.


Bodybuilding: Increase size without sacrificing definition

Disclaimer before reading: If you have questions about your health, you should consult the advice of a medical physician or professional. Also, I encourage you to do your own research! If you want to know more about a supplement, muscle group, or workout routine, try searching it on Semantic Scholar, Google Scholar or MIT’s Web of Science to learn more from actual publications – not advertisements!! Note that MIT’s Web of Science is filtered (typically articles are from journals, not pdf’s of a website that might end up on Google Scholar).

Disclaimer 2: This article was written by a younger, more exuberant version of myself. Excuse (or enjoy) my tendency towards over-excitement, exclaimations, and the like :)

All of the information presented here is distilled from academic sources at some level, however keep in mind that nutritional claims are typically limited. Many nutritional studies can at most claim that if you take a random sample of N people, nutritional supplement X will improve something, on average, among the N people. Nutritional studies rarely claim that if you take supplement X, supplement X will work for you. We are still decades from having a complete model of every process in the human body - therefore we can not make true predictions about the output of the human body as a system, given an input, supplement X, to the system. If you stumble upon such a model, do share, as I’ll be happy to accept the Nobel Prize in Medicine/Chemistry with you.

Typically, bodybuilders struggle with a common conundrum. To get big, you have to eat big. But when you eat big, you lose definition. How is one supposed to continually gain muscle mass, while remaining ripped/cut (i.e. extremely low body fat)? The common trick is to BULK, CUT, BULK, CUT, etc. In other words, you spend 4 months bulking (lift big, eat big) - and yes, you do gain some fat, but you also gain considerable muscle mass. Once you have gained (e.g. 20 lbs = 15 lb muscle gain + 5 lb fat gain), you CUT by greatly reducing your food caloric intake and increasing your cardio/endurance training. Losing some muscle mass is unavoidable, but you will typically burn/lose more fat (e.g. 7lb fat loss, 3lb muscle loss). Now you are leaner and stronger. And the cycle repeats…

Although BULK-CUT is arguably one of the faster (and most common) ways to get big (increase muscle mass) and ripped (maintain low body fat) at the same time, this up-and-down cycle can be difficult for many weightlifters/bodybuilders. Firstly, it requires constantly changing your lifestyle and eating habits. Secondly, it requires sacrificing your toned physique towards the end of the BULK phase. Thirdly, cutting too many calories can stunt your metabolism, preventing you from losing weight. Instead, I present a supplement / workout regime which allows you to gain muscle mass while maintaining low body fat, at the added expense of increased effort, endurance/cardio training and added patience. To mitigate the increased intensity, this regime prescribes a strict supplement intake that will boost you through to success by optimizing the “muscle growth” / “power expended” ratio.

The most important thing is to stick with it. 90% of people who start working out quit in the first two weeks. This is one of the saddest self-crimes one can do. Why? Because two weeks of hard works is now wasted and if you just hang in there a little longer, after the first month, you’ll start to notice the benefits…. improvement in size, muscle definition, overall health, alertness, mental clarity, endorphin release, libido, and overall moral and confidence. These benefits are just the “pick-me-up” you need to keep going. After 3 months, you’ll notice dramatic improvements. If you don’t, then your money back… oh wait, I’m not charging anything.

Always keep in mind, what works for me, or for your friend, or for the author of the article you just read… might not work as well for you. You must experiment to figure out what works best for you. Try new things, add variations to your workouts, read contradicting articles, experiment, experiment, experiment. Why? Well beyond figuring out what works best for you, it’s a great way to keep your routine an exciting part of your day and something to look forward to.

Finally, for beginners, ease into it. Start with lighter weights than you think you can do for the first month. Before workouts, don’t be afraid to warm up with light push-ups or stretches. Going from zero workouts, to intensive working out will be a shock to your body. Be good to your body and ease into it, slowly increasing the weights as you become comfortable with the motions of the exercise.

Perfect form during an exercise is nearly always better than lifting a heavier weight.

Let’s begin.

To get both bigger (increase muscle mass) and toned (decrease body fat), you will benefit most from four things:

  1. Strength training
  2. Cardio/Endurance training
  3. Nutrition (eat well / supplements)
  4. Sleep (as much as you can, if/when you can)

A good workout should:

  1. Be switched to a new workout after 4-6 months.
  2. Some kind of running/swimming/stair-stepping/biking/etc.
  3. Alternate muscle groups (e.g. never follow a tricep exercise with another tricep exercise unless you are going from a compound exercise to an isolated exercise or in some advanced workouts, vice versa)
  4. Not necessary, but try to have some minor variation (grip, stance, duration of each exercise) week to week.

Arnold’s Workouts:

Other than perhaps theoretical computer scientist Manuel Blum, Arnold Schwarzenegger has always been a role model for me, along with about a 100 million other people who go to the gym. That’s because Arnold completely changed the game of weightlifting and bodybuilding - dominating Mr. Universe for nearly a decade, before becoming one of the most famous actors of all time, and then serving as governer of California. Recently, in partnership with, Arnold released his blueprints for working out. The goal is always the same – GET BIG, GET CUT. He released his workouts seperately, and they are meant to be cycled. 8 weeks of growth, break for a week or two, then 8 weeks of cutting. Beware! these workouts are intense! Don’t start here. But if you’ve already been working out for a few years, and you want to see a next-level-of-progress, these two workouts will change the way you think about working out. I’ve done both and I’d argue they are a bit old school - they don’t cover the full range of motion of every muscle, and they are full of redundant repetitions instead of variation. However, it does work. You will get bigger. You will get more cut. Just remember to add stretching and warm-ups, which aren’t included in the workouts. Cycle:

  1. Arnold’s Blueprint to Mass Workout
  2. Arnold’s Blueprint to Cut Workout

How to increase the weight:

If you wish to continually increase your muscle mass, you’ll need to lift heavier weights. Once you’ve maintained a certain number of repititons at a given weight and exercise for at least 3 weeks, try to increase the weight. A common trick to help you increase weight is to reduce the reps, then work your way back up. For example, if I lift 10 reps on bench press at 100 pounds, then to increase my weight, I’d start lifting 6 reps on bench press at 110 pounds. After a couple weeks, I’d lift 8 reps at 110 pounds, and then a couple weeks later, 10 reps at 110 pounds. Then the cycle repeats.

Protein Types and Usage:

Try to consume 1 gram per body weight per day. Four main types: Whey, Casein, Egg, Soy (also pea, oat, rice proteins, and more).


Take Whey 30 minutes before and right after workout. Sometime later (2/3 hours) take casein or egg. Take casein or egg before sleeping.


Whey is quickly absorbed into the blood and causes a huge spike in amino acid content in the bloodstream and therefore protein generation 20-40 minutes after ingestion, but does not inhibit catabolic processes (muscle breakdown). However, some research has suggested if you keep taking whey over and over, you will stop producing protein at that rate. Casein and egg break, however, provide a slow digesting protein (constant steady small amount of amino acids available in bloodstream for about 8 hours) that will prevent muscle breakdown. If you take casein&whey together, the casein or egg will prevent the whey from being digested - so DON’T do this! Take whey post workout, then casein/egg sometime before bed.


  1. Whey - Good for post workout. Causes huge spike in protein synthesis 20-40 minutes after. Doesn’t prevent muscle breakdown.

  2. Egg/Casein - Good for protein synthesis (minimal) for 8 hours. Prevents muscle breakdown. Causes whey to digest slower if taken together (reduces muscle growth - so don’t take them together, take egg/casein at night).

  3. Soy - Much research suggests that soy reduces sperm count and testosterone levels in men, but the protein is fine. Although keep in mind most soy beans have been genetically modified. (As if cows haven’t been… the same cows that produce the milk that whey and casein come from. So good luck here.)

Supplement Timing:​

In morning, (or spread throughout day) take these supplements:

  1. Workout performance vitamin(s) (not a lame general multi-vitamin)
  2. 2-3 Fish oil capsules
  3. 1-2 Glucosamine pills

Before and after workout, consume (use recommended dosage on bottle):

  1. Whey Protein (take alone in morning as well)
  2. Creatine
  3. Beta Alanine
  4. BCAA (branch-chain amino acids) only right before workout

Before sleeping (very important):

  1. Casein protein in water

What does each supplement do (in order of importance):

Whey protein (take before and after workout and when wake-up): This is the most important supplement. I recommend never heavy weightlifting without consuming whey protein before and after a workout. This is how you re-build muscles. No protein –> no muscles. Working out without it, just means you burn fat, but won’t build muscle unless you consume extreme amounts of protein from your food, and still you will not build muscle as well without whey. This is because whey, when consumed before and after a workout, creates a spike of amino acids in your blood stream right at the time when your body is healing/building muscle. Most foods with protein break down slowly and don’t provide enough amino acids immediately at recovery time after a workout. Whey is the single most important supplement. (If you’re a man, avoid consuming high amounts of soy protein - some studies suggest soy may reduce testosterone and sperm count).

Fish oil (take in morning or throughout day): Fish oil contains omega-3 fatty acids. There is a wealth of literature promoting the benefits of fish oil and omega-3 fatty acids. I will list a small sample of what can be found by searching any repository of nutritional articles. Some of the believed benefits of fish oil are improved brain function, recovery, less soreness, better metabolism, likely reduction in cancer, improved skin and hair, improved heart function, improved joint function, promoting fat loss, and more.

Some nutritionists believe that you should consume two sources of omega-3 fatty acids since some forms may be more easily digestible than others. Because of this, I recommend also consuming either ground Chia seed or ground Flax seed. The seed should be ground since it is difficult for your body to digest the seed if the outer shell of the seed is intact during consumption.

Workout vitamin (take in morning or throughout day): Unless you have access to hundreds of food options, three meals a day, a good workout vitamin is a great way to make sure your body is getting everything it needs, everyday.

Some highly effective workout vitamins to purchase are:

  1. RSP Nutrition BioVite multivitamin
  2. Optimum Nutrition Opti-Men / Opti-Women

Workout vitamins are essential for overall health and recovery. Workout vitamins typically include things like green tea extract and other natural extracts which collectively had a variety of health benefits beyond the vitamin and mineral content.

Pay attention to how your body reacts to these things. If you find yourself having to pee every 15 minutes, you probably are taking too much of something and that’s your body’s way of getting rid of it. This can happen for example if you take a workout vitamin with 100% of your daily value of vitamins/minerals, then you also eat a large bowl of cereal (that contains 100% DV vitamins) plus drink some drink/shake (that also contains 100% DV vitamins) – this is not good! Don’t do this.

Greens Supplement (in morning or as directed): Greens supplements ensure you consume a full day’s worth of the most healthy vegetables/fruits, everyday. These supplements contains everything in vegetables/fruits that the vitamin misses. This is essential for healthy living, not just bodybuilding. Check out PharmaFreak or GreenGrass.

Creatine (take before and after workout): Creatine does three main things:

  1. Increases size of muscles and strength (but you must drink more water!! Creatine requires more water)
  2. Huge boost for muscular endurance
  3. Huge boost for muscle recovery

Creatine is naturally occurring and produced in the body, however our processed foods, meats, and overused soils don’t provide the amounts needed for optimal muscle growth.

Beta Alanine (always take with creatine before and after workout): Beta alanine does not increase size, but you’d be remiss not to consume it before and after workouts.

Among other benefits, beta alanine purports to:

  1. Allow you to sprint faster, push harder, explode stronger - overall workout performance boost
  2. Provide a huge stamina boost, boosts muscular endurance
  3. Improve workout performance
  4. Delay fatigue so you can keep killing it in the gym until your workout is over

However, beta alanine requires a build-up in your system. You need to take it regularly for 1-2 weeks before you’ll notice effect.

Casein Protein (take with water after workout if possible and always before bed): When you sleep, your muscles break down because you are not eating. Therefore there are no amino acids available to maintain muscle growth and mass. Casein protein breaks down slowly and provides amino acids in your blood stream for up to 8 hours, greatly reducing “muscle starving” that causes your muscles to break down over night and become weaker and smaller. This supplement is essential for maximal growth.

BCAA (take just before workout and when wake-up): The Branch Chain Amino Acids are the main amino acids your body actually uses for recovery during and after a workout. Taking these just before a workout will:

  1. Promote muscle growth and recovery,
  2. Help with strength and power during a workout

Glucosamine (take in morning): Glucosamine is extremely important for joints and tendons. Its primary purpose is for joint recovery (preventing the pain caused from working out over the years), but it has another important purpose. Bodybuilders who have been lifting weights for over 10 years may suffer from a variety of joint and bone issues due to the high chronic stress on these areas. Glucosamine is a long-term preventative supplement which aids in maintaining bone and joint health with continual weight training. You may not appreciate it today, but you will in twenty years. Additionally, if you went to the doctor with natural joint pain, glucosamine is a standard recommendation. If you are suffering from joint issues, you should of course seek the advice of a medical professional.

Bonus – Sleep:

If you’re trying to get ripped and add muscle mass, you’ll need more sleep. Stop trying to get around this and accept it as fact. If you don’t sleep enough, you won’t get stronger.

Bonus – Eat healthy:

Increase intake of:

  1. protein – Somewhere between 0.5 grams to 1.3 grams per pound of body weight per day, depending on how much you’re working out. For example, I weigh ~175lbs and aim for ~150g of protein.
  2. fiber – Aim for 20-30g per day. High consumption of protein powders is like pouring sand into your sink – fiber + water helps move this stuff through. Just trust me on this one and do your digestive track a favor – eat lots of fiber!


  1. sugar – try to NEVER eat foods with added sugar – candy / soda / juice with added sugar
  2. fat – try to NEVER eat saturated fat, a little unsaturated fat is okay - avocados / fish oils / etc
  3. salt – This is a big one - too much salt decreases your muscle’s weight to power ratio.

It really just comes down to eat protein and fiber. Avoid sugar, fat, and salt.

For more information, here are some (mostly non-academic) other sources: