Yearlong Soylent Experiment

I have no basis beyond my own personal gauge of how I feel and function. I haven’t seen any doctors or done any official tests. But, then again, I never did any before going on Soylent either. Anecdotal feedback so take this for what it is. I thought my experiences with Soylent here could be of interest to someone.

I switched to a ~99% Soylent diet near the beginning of March last year. I stayed as consistent with it as I could. Back then it was Soylent 1.4. After just a week, a week and a half, of nothing but Soylent I felt great! (Aside from some acidic bowel movements but those were quickly resolved by taking the psyllium husk suggestion in these forums) I had more energy, my rests were shorter by much more restful, I had better performance at the gym in my workouts, I felt like I could concentrate better than ever… it was as if I was getting proper nutrition for the first time in my life.

But then the switch to 1.5 happened. It took a while but maybe a month or two before switching to 2.0 when it released, what, a month early? I began to feel more and more lethargic. It was so gradual that I didn’t really realize how bad it was getting. Was my body getting too used to Soylent? Was it some change from 1.4 to 1.5 that wasn’t agreeing with me? I don’t know what happened and I barely noticed, just living day to day doing my thing.

I jumped on the 2.0 train because I loved the idea of the improved convenience it promised. I liked the taste of 1.4 better than 1.5, but 2.0 has definitely been my favorite tasting Soylent. But when it came to how I felt, my energy, my performance physically and mentally, it was still slowly declining. And I still wouldn’t really notice a change until recently because of how gradual it was. The switch from “normal” healthy diet (lean meats, vegetables, no processed foods, water as only drink) to all 1.4 had me feeling amazing for months. With a huge leap the first couple of weeks until it was more gradual. Maybe because my physical and mental performance had improved so it was helping to naturally improve myself further. 1.4 to 1.5 I didn’t notice the change until I started 2.0. First week or two I noticed my performance at the gym was gradually decreasing. Like just before switching to 1.5 I worked my way up to being able to do 12 pull-ups. A personal record! But at the end of 1.5/start of 2.0 I was doing well to get 3 or 4 in. I shrugged it off as just a bad day, everyone has those, but I could never get back, never improve. Then in late November, early December I noticed I was having trouble focusing. I was lucky enough to start a new job the first week of November but I still find it difficult to focus as well as I want to, as well as I remember being able at the height of 1.4.

Mid January I decided I needed to make a change again. I knew my one year experiment I put forth for myself to go all in on Soylent, so see if the calorie and nutritional control would help. It seemed to help very well for a while. But assessing how I’ve been feeling the past few months… lethargic, tired, having difficulty thinking and processing things to the point of taking noticeably long pauses before I speak… I dunno, I feel a far cry form how amazing 1.4 initially had me feeling. I feel as if I’ve slipped backwards so much.

Since the year experiment is nearly over I’ve decided to end my time on Soylent and switch back to a normal diet after I finish my current supply of 2.0. I plan to see a doctor as well just in case it could be something else beyond diet. fingers crossed it’s just the 1.5 and/or 2.0 formula that didn’t agree with me.

Extra note: I supplemented my workouts with post-workout protein and pre-workout BCAAs and all that supplement jazz through cycles just as I did before switching to Soylent.

I’ll still try and keep abreast of the goings ons with the company and product. I believe in them and want to support them, but if turns out it isn’t right for me then it isn’t right for me, yeah?


I’m not trying to talk you out of the idea that a 100% Soylent diet isn’t for you, but it might be worth looking at other changes in your lifestyle aside from switching Soylent versions. The job change is the one that leaps out at me: are you working longer? Working harder? Working differently? Under more stress?

Sounds good that you’re going to see a doctor, I hope you’re okay. The drop in the number of pull-ups you can do sounds worrying/interesting. Did you get heavier over the same period?

1 Like

So did it help in gaining muscle mass? Or did you slim down but get lean?

For your 1.4 experience, did you take the initial euphoria under consideration ? I’m talking about the effect of being slightly “high” after implementing diet/lifestyle change.

I felt this (while being aware of it) when I started on 1.4. The “increased energy and focus” eventually wore out, but not to the point of feeling lethargic or weak. It was probably caused by Soylent straightening out routine, high quality nutrient delivery, plus shifting energy source from sugars toward fats. I noticed no change on 1.5.


It’s actually a less stressful job, if you can believe it. Better, more consistent hours. Before I could work 12 hour days. Now I’m on a consistent 8 to 5. And my weight stayed roughly the same. I’ve actually lost muscle mass in the last few months. I’ve attempted to adjust my supplement intake accordingly but with no results. Although the decline came before the job. Though stress over getting the job may have played a part at that point, won’t rule it out. I’ll keep this in mind when I do see a doctor. A good point, thanks.

1 Like

When I first switched to Soylent last year I noticed an increase in muscle mass and strength. I felt great. I grew to where I was able to lift heavier and harder and my large were larger and toned. But now they’re, like, noodles. I’m shocked it took me so long to really notice. But maybe when you’re not feeling well you’re not very observant sometimes.

1 Like

It sounds like waning excitement to me. Double blind studies are double blind because placebos can have statistically significant effects on people. Despite people’s excitement about Soylent’s “perfect” nutrition, it really is just food. Our bodies are very capable of being very healthy or very unhealthy whilst consuming a well balanced diet or a randomly varied diet. The main problem arises from prolonged unvarying diets that are lacking essential nutrients, such as with the kid who was hospitalized after eating practically nothing but chicken nuggets for 15 years.


This is definitely a thing that happens. My Soylent experience began with DIY a couple years ago, and for the first two or three months I lived on it almost exclusively and felt great. Then at some point I stopped feeling full, no matter how much I drank. I’d chug a blender bottle-full before bed, then wake up hungry at 5AM and chug another one. I changed up my recipe several times, but the window between the recipe changing and me feeling hazy and hungry got smaller and smaller each time, until eventually I gave up and went back to solid food. This has happened to me with most of my dietary staples (before Soylent it was oatmeal, trail mix, eggs, vegetables, etc.), so I think there’s just something that happens when your body is digesting the same thing all the time. Like @varialus said, Soylent might be less stressful than solid food, but it’s still food.

Now I use 1.5 for probably 60% of my calories (flavoring it differently every day to avoid getting sick of the taste), but I still eat a hot meal for lunch and dinner whenever I can. It’s crazy - Soylent keeps me full and focused in a way that something like oatmeal never could, but as soon as I take that first bite of BBQ or pita or whatever I’m having for lunch, I feel more awake, my sinuses clear up, I can feel my muscles relaxing… it’s like my body hasn’t quite woken up until I give it something solid to digest. I’m actually surprised (and kind of jealous) that a 100% Soylent diet works for anyone, but maybe some people’s metabolisms are better geared to eating the same thing all the time than others.

1 Like

I think something like “conversion syndrome” happens to many people who start drinking Soylent. I have seen many people report mysterious bursts of energy that I thought were ridiculous right here on this site. I think that reported declines in energy are also ridiculous. People convert to a new religion and suddenly everything seems solved. Then the novelty wears off.

I myself have started getting interested once again in the theories of doctor Furman, author of Eat to Live and other books. But I think I’ll stay with Soylent also for a long time. Just not as close to 100% as I have been.


I have some friends that swear by Dr. Furman and made some gains, only to fall off the wagon… While I could adopt some of his teachings, I could never follow it to the letter.

Does that effect last for months? I remember feeling great for all 4 to 5 months I was on 1.4. And the decline was so gradual I don’t know when it really “kicked in”.

It did feel like I suddenly had a burst of energy 1 maybe 2 weeks in. Though that burst didn’t wane until I guess a month into 1.5. Would something like conversion syndrome last that long?

Well, in religion I think it could last for years. Everyone’s psychology is unique. Consider bad marriages, for example…

1 Like

Glad to hear your work situation’s improved. I can totally believe it — things can get better!

Not being able to lift as much weight as you used to sounds like a fairly unambiguous indication that something has indeed changed. Just to rule out the obvious, did you reduce your exercise frequency for a while? Or stop exercising for a week or two? I always find that a few months of consistent exercise leads to noticeable improvements in performance, and a couple of weeks off makes me feel like most of those improvements have just evaporated.

1 Like

It may be seasonal affective disorder. The fall and winter, I feel like that. Could be a bout of depression.

1 Like

Thanks for detailing your experience, it was a great read. The transition from 1.4, 1.5, 2.0 show a consistent lower of fast digesting carbs, which are well known for energy bursts/mood altering. And I have had misgivings about soy products. I expect you are done with Soylent, but what I would find interesting is a transition back to 1.5, to see if any of your effects reverse. In my mind, it would answer many questions.

How has your sleep been?

1 Like

I’m with TTE, I do about 60% to 75% Soylent 1.5. I find moderation still really helpful, and after having a meal or two as epic enjoyable food, which is usually social eating, I find having a meal of Soylent is really nice again.

I wonder if OP’s initial improvement was also his body reacting to having carbohydrates again. I’ve heard a couple stories of people on a full paleodiet that take their cheat meal and then have the best workout of all time. Carbs are fuel, people should let their bodies run on them occasionally.


I am a Senior at The University of Alabama and current major in Food and Nutrition.

You made it through an entire year! That’s awesome not many people can actually say that. This past February I also began a one year meal replacement experiment, starting with Joylent for six months than moving on to Pulve. (I live in Europe, Soylent is unable to ship out here yet).

For my occurance I am using a blood glucose machine to monitor my sugar levels. This is a bit different than going on feeling alone. As an example I have been on the experiment now for over 3 weeks and I noticed that my blood sugar levels have stabilized (when compared to previous readings). Before I began the experiment, I would have afternoon dips around 3pm, now I do not anymore. I could attribute this to my blood sugar levels stabilizing.

Regarding the fatigue and loss of muscle mass, within the nutritional realm there are two type of deficiency causes. The first is called a primary deficiency, there is where you lack a certain micro/macro nutrient through not eating enough of that particular nutrient. The second is called a secondary deficiency, there is where something other than diet is to blame, such as a disease or metabolic process. The only true way to find out is to go see you doctor for various health screens.

Pauldwaite was correct to say that so many things can effect our bodies natural rhythm. Anything from lack of sleep, to stress and even seasonal changes all can have a lasting impact.

Another thing that’s possible is the power of persuasion, I still feel like I have alot more energy from eating Joylent, but it’s hard to tell, is that is just a placebo effect? Visually I look at the packing and I can see that on paper it covers all the bases. It gives me a certain level of comfort knowing that. Could this be where the sense of having more energy comes from? possibly so… At the three month mark I will undergo a second set of blood serum level testing, and again at the 6th month mark, to compare against my original levels.

If anyone would like to have the link to my blog regarding The One Year Meal Replacement Experiment let me know. I did not post it on here as these Soylent guys get a bit ruffled when it comes to outside links to competing companies.

I hope your energy levels return back to normal, and wish you the best of health!


I went to the doctor back in August when I was on my eat whatever my heart desires diet. Will go to the doctor here in 2-3 weeks. Have been working out and drinking Soylent and Ramen/Soups. I was healthy before but will see if I remained healthy, became healthier, or gotten less healthy.

1 Like