A couple of very important points of discourse on the subject of under eating, or as I prefer to think of it, "under fueling".
If you are training for improved performance in sports and / or a change in body condition, it is crucial to exceed your minimum requirements in total energy and protein intake.
Under eating will not cut it.
You cannot facilitate the changes in body condition you are trying to produce without providing the necessary resources. You cannot starve yourself into strong, healthy, athletic shape. You just can't.
This is a double edged sword though, as attempting to under fuel often results in involuntary over eating later on.
This is an easy situation to fall into, but fortunately just as easy to avoid or to rectify. Simply, by setting a meal schedule as best suits you in order to ensure that your energy and other nutritional requirements are met. Your psychological needs are of no less significant importance here, as well. Set a schedule, have a plan to meet and exceed your minimum requirements, and stick to it. Set the alarm on your phone to remind you when it is time to eat, if necessary.
No more working through lunch or skipping meals for other reasons.
You need to eat, god dammit.
Having a meal schedule and especially as part of a larger plan to meet some appropriate total energy and macronutrient intake targets also means that you are more mindful of how much and what you are eating, as well. As much as I do believe habitual under eating is a serious and widespread problem, at the same time there are no shortage of people who are under the assumption that they are "probably not eating enough" who are actually massively over feeding.
Regardless, having a schedule, appropriate targets, a plan and the intention of sticking to that plan as consistently as possible will solve either problem and many others as well.
Under eating due to restriction of food choices.
A second cause of under eating can be restriction of food choices. Too often, proponents of certain diets advocate the exclusion of various food choices which can be advantageous in meeting both your micronutritional and total energy requirements. Even so called "empty" calories from more indulgent choices of foods are not inherently bad if they prevent you from falling short of your energy requirements where you would be likely to otherwise.
Nutritious foods such as cereals, breads and other grain based foods do provide significant micronutritional resources as well as valuable energy. There is no need to restrict or eliminate intake of these foods, other than as necessary to manage a medical condition that you actually have. Not a medical condition that may hypothetically exist according to alternative health bloggers, not even one that someone told you their cousin suffers from, or whatever else. Unless you have been advised to do so by your doctor or dietitian to manage a diagnosed condition that you actually have, there is no need to cut out grains or anything else that you enjoy and can utilise as a source of energy and other resources to meet your requirements.
Now, usually when there's a debate on this matter... the argument is that people can just meet their energy or micronutritional requirements from other foods, instead. This is true. Will they, though? For many people who find the "other", suggested foods less enjoyable or less appealing, they simply won't eat enough of them. Rather, they just end up not eating anywhere near enough in total, due to having cut out the foods that suit them best for no good reason whatsoever other than bad advice and pressure to conform from people who lack the basic empathy to understand that different people will prefer different foods and that is ok.
Any advice that suggests, advocates or inadvertently results in habitual under eating is terrible and potentially harmful advice.
