Irritability is not the only emotionally related issue linked to a “fat free, higher carb” diet, depression, is another factor tied into not eating enough or the right balance of fat.
This is true especially if you are a convenience food consumer.  Why? Because, trans fat (the ingredient used to replace real fat in real foods so you are not deprived of foods that taste good) has also been linked to depression, http://www.medicalnewstoday.com/articles/215021.php.  Here are some links if you want to find out where trans fats are lurking, http://www.huffingtonpost.com/2011/12/06/trans-fat-foods_n_1130573.html and http://www.acaloriecounter.com/trans-fat-foods.php, http://www.acaloriecounter.com/fast-food-trans-fat.php. 
Fat is involved in nerve impulses, the production of brain chemicals and hormones (for both men and women). So when you avoid fat, risks for ADHD and many other brain health issues as well as eating disorders because the nerves, hormones and brain chemicals may not function correctly.
Fat soluble vitamins: A, D, E and K, along with vitamin B6 and B12 (abundant in red meat and fish) are important for  growth, immunity, cell repair and blood clotting and so much more. If you’re not eating enough fat to for these fat soluble vitamins into your body, they will be excreted, and you may be at risk for a vitamin deficiency. Vitamin D deficiency alone has been linked to:

• Increased risk of death from cardiovascular disease
• Cognitive impairment in older adults
• Severe asthma in children
• Cancer

In fact, research suggests that vitamin D may play a role in the prevention and treatment of type1 and type 2 diabetes, hypertension, glucose intolerance, and multiple sclerosis.
Additional health conditions that are catapulted by high carbohydrate foods that directly impact insulin and blood sugar spikes are:
Metabolic syndrome
Heart disease
PCOS
Cancer (Colon, breast, and prostate) are associated with low intakes of essential fatty acids
Yeast overgrowth
Dental caries
Advanced glycaction endproducts (AGE’s), contribute to the aging process as a result of excess sugar (again I remind you, 100% of carbs converts to sugar) http://www.prevention.com/node/23567#ixzz24u7nJ8SU. 
Adrenal dysfunction and defects with cortisol release

As I realize that there is just so many reasons to limit carbs, I am going to ask that you read the information that was written in 2004 by Kent Rieske entitled, “Scientific Proof Carbohydrates Cause Disease” posted on Dr. Mercola’s website, http://articles.mercola.com/sites/articles/archive/2004/01/03/carbohydrates-age.aspx.

 And now I am off to write more on this and will move on to reasons # 4 and 5 to “Eat Foods With Fat”.

 Related articles
How Fructose Turns on your Fat Switch, http://lewrockwell.com/mercola/mercola220.html.