I've written about the late Seth Roberts, who was famous for self experimentation. Jimmy Moore has also published results of his experiments to reduce and maintain weight and good health. Paul and Shou Ching Jaminet also advocate self research in finding your way to optimum weight and good health.
The gold standard for scientific research is the randomised controlled trial. A statistically significant number of people is divided randomly into two, one group is given the variable (drug, food, other intervention) and the other group is not. The second or control group may be given a placebo pill, food or other intervention. Those assigned to each group are numbered and recorded. The aim is to ensure that neither the test subjects or those working with them know who has the intervention and who does not. This prevents the researchers and test subjects from skewing the results. It also eliminates confirmation bias, when humans seek and find results that seem to confirm what they believe.
Using yourself as a test subject is open to criticism, because an individual result cannot be generalised out to the whole population. On the other hand, it can be useful for the tester to help find solutions to their own health problems not provided by health care professionals or over the counter drugs. There is even greater risk of confirmation bias and other distortions creeping into n=1 experiments. Humans are notoriously unreliable when remembering the past and liable to make post hoc rationalisations.
I was asked to participate in trials of a sleep device. The questionnaire was detailed in asking for feedback on what happened AFTER I tried the device. It was open to criticism, because it stopped there.
In my view, we need to be systematic in experimenting on ourselves. Here's my list of things to include when trying out something to improve health, weight or fitness:
1 Keep a notebook or file on computer detailing what happened
2 Before starting the experiment, note down your history of this topic (weight loss, insomnia, low mood or whatever) to get a baseline starting point. Record previous attempts to improve the situation and interventions used as well as your views about factors affecting your progress
3 Start the experiment
4 Identify ONE intervention and make every effort to keep the rest of your life as consistent as possible (eg add more fat to diet or wear orange safety goggles). Avoid adding other NEW changes to diet or lifestyle. If you make multiple changes, it's impossible to determine what has caused improvement/deterioration/no change in your state.
5 Note the results each day. Record numbers wherever possible (eg weight loss/gain; amount of time it took to fall asleep, time slept - light/deep/dreaming sleep, amount and quality of dreams, times woke during the night, time taken to sleep again etc)
6 Record other factors that may have affected progress as well as other notable things (eg external events affecting sleep/stress).
I've run experiments on myself and kept note of food intake, body composition, blood glucose, blood pressure and sleep patterns. I've noticed how difficult it is to draw definite cause effect conclusions, but have made tentative guesses, often with multiple potential contributory factors (particularly to insomnia). This helps me to avoid over confident generalisations or assertions and focusses my attention on areas for further investigation.
I've encouraged clients to use self experimentation and notebooks, arguing that these are much more persuasive with their doctors than verbal reports, particularly when GPs dismiss weight loss problems as chronic overeating. This gives them more confidence in dealing with their own health and communicating with their doctor.
You may not find a single solution, but will gain a clearer sense of your own metabolism and what helps and hinders progress. I still have insomnia sometimes, but recognise the contributory factors and how I can limit them.
Postscript: It's useful to identify your goal prior to self experimentation. For example with insomnia you may want to fall asleep sooner or sleep longer, rather than waking up in the early hours of the morning. You might want to have deeper sleep. If you know where you want to go explicitly, it's easier to track progress and alter your experiment later on.