Lovely to hear from you and thanks for your question. As a naturally slim dood myself it’s an issue I deal with also so I can empathise with you.
These things are impossible to answer definitively via email, because as with every situation, it all depends on one’s individual body type/constitution, lifestyle demands, state of balance or imbalance etc and a host of other factors.
Some general points to consider however are;
1. Eating light at night is a relative concept. If we are genuinely hungry, the body wants food and thus it is okay to eat. Generally though, the later at night it is, the smaller/lighter the food should be. However, working on computers late at night is an aggravating factor. It tends to overstimulate the nervous system and thus we can think we are hungrier than we actually are. I.e. it is an emotional or stress-based hunger (from excessive nervous system stimulation or what’s called ‘Vata-aggravation in Ayurveda) rather than a genuine stomach or physiological hunger.
2. The simple idea with light dinners, is that dinner should be satisfying enough that we don’t feel hungry or undernourished during the night, but that it’s light enough that we have largely digested whatever we’ve eaten by the time we go to sleep – preferably early!
3. A key point in the whole discussion of ‘light dinners’ is that they are not recommended as a ‘weight loss’ remedy perse. The timeless wisdom of Ayurveda, outlines how eating light at night is in tune with the eternal, natural cycles for all-round health and wellbeing – weight loss, where it’s needed, is just a natural by-product. The main problem with your current outine is that by staying up so late you are violating one of Mother Nature’s most fundamental natural cycles, and thus any dietary or other changes you might make are a bit like moving the chairs on the Titanic.
* As my gift you can download the entire 2nd chapter of my book which discusses the daily cycles in detail. As you’ll see there’s generally speaking no such thing as human ‘night owls’ … at least not in a long-term healthy sense, and so many other critical benefits to getting to bed ‘earlyish’ (including normalising body weight … whether reducing or increasing).
4. Due to our Western culture of having our main meal in the evening, most of us have been conditioned to thinking that we need more food at night than we actually do.
For your particular situation, the reality is that going to bed so late is most likely not conducive to optimal health in the long run. (You are some way towards a shiftwork routine which is certainly not ideal and needs a specialised approach.)
Similarly, the related issue of being underweight may need to be addressed separately, assuming you are actually underweight – you may just be naturally superslim, I don’t know. Genuinely being underweight can have many causes, e.g. due to excessive mental or emotional stress, and most commonly due to problems with digestion. If the digestive system is blocked or stress is preventing it from working properly, no amount of food will lead to ‘healthy’ weight gain. Without knowing your situation, assuming the above issues are not relevant, focusing on getting home earlier and not working on computers so late at night would probably be your best focus. Once the body comes back into balance, then eating nutrient dense, nourishing foods during the day (which is when the body is naturally designed to digest and assimilate nutrients to build up healthy tissues and thus establish its natural, healthy body weight) will tend to have the best results.
Remember also that lack of sufficient, quality sleep can also be a major factor in weight problems (either overweight or underweight), as between 10pm and 2am is when the body is designed to be regenerating and nourishing itself internally. Focusing on getting to bed earlier, gradually over time, and eating earlier in the evening should bring significant benefits to your overall health. If you are genuinely hungry before you go to bed, then simply ‘eat more at dinner’ (remember light dinners are relative to how quickly you digest them!). If you are still hungry later on for some reason, and it’s not just an old, conditioned habit, then by all means have something light. Yes, goats milk kefir if warmed is a great option. If you have trouble getting to sleep, a pre-bedtime warm, full-cream, unhomogenised milk with spices may be even better – see ‘Medicated Milk’ recipe.
Finally, be careful you are not eating just because you feel you are underweight – whatever we eat has to be properly digested, otherwise it will produce what Ayurvedic medicine calls ‘ama’ (undigested food) which creates long-term problems. Eating for ideal health and what makes us feel good is more important than eating to increase or decrease weight perse. As I always say, “be healthy, and let your body work out what is it’s ideal weight”. (This article discusses why health is more important than weight – good in theory at least.)
I hope all this helps somewhat and good luck with everything.