If you are on a weight loss spree, chances are that you are on a calorie-restrictive diet. Gorging on low-calorie salads and soups and skipping a few meals can help you knock a few pounds. But in the long run, not having enough calories can have catastrophic consequences on your health. These bodily symptoms are signs that you are not eating enough.
You are tired all the time: This one's a no-brainer. If even doing simple household tasks wears you out, you probably need to eat more. Being fatigued all the time is a sign that your body lacks fuel to up the metabolic rate. Studies show that one of the causes of fatigue is inadequate intake of calories.  
You are forgetting things: Erratic dieting that is deficit in calories has been linked to impaired cognitive performance and memory. If you find yourself misplacing your keys or forgetting the name of your co-worker of three years, you could be facing a calorie deficit.  
You are losing hair: The colour, texture and thickness of your hair are all directly proportional to your health. No wonder the hair is called the barometer of human health.   
You are frequently hungry: Another obvious sign is that you stomach is always growling at the thought of food. Restricting calories can cause ghrelin and leptin, your hunger hormones, to go haywire. This could trigger binge-eating episodes and weight gain. 
You are gaining weight around the belly: Strangely, not eating enough could make you gain weight. Low calorie dieting causes your stress hormone cortisol to go up. The hormone is notorious for causing weight gain in the midriff area. 
You are always cold: Are you always the only one in the room who wants the AC switched off? It could mean you are not eating enough. Long-term malnutrition and calorie restriction is known to lower your core body temperature. 
You start missing your periods and can't get pregnant: Before you start suspecting a possible pregnancy, your missed period could also be a sign of your poor eating habits. Eating a nutritionally-deficit diet can cause amenorrhea or no menstrual periods in women. In the absence of ovulation, women have a hard time getting pregnant. 
You are always irritable: Ever tried talking to a hungry person? You are right. They are always cranky. Science says that not eating enough can cause apprehension, irritability and overall mood swings.