How much is missing in calories in an ALS patient's diet?
Half of the ALS patients have a condition named hypermetabolism 
You can ask to your doctor if this is your case, there is a simple test that can determine this.
When someone have this condition their diet should bring more energy to compensate the increase in energy needs due to hypermetabolism
This calculator helps to quantify how much energy is needed for this ALS patient
It uses two formulas, one named Harris-Benedict  to calculate the needs in calories for a healthy person.
The second named Kasarskis , calculates the needs in calories for an ALS patient.
This calorie loss translates into weight loss .
This calculator does not store any data.
I am not a medical doctor, nor a scientist, so if you have any medical question, ask to your MD!
However you can contact me at this email address: contact at padiracinnovation.org
For example, a rapidly progressing male ALS patient is 60 years old at the time of diagnosis.
His height is 70inches (178 cm), his weight is 180lbs (82 kg), so he is initially overweight.
The first year he lost 7.9 kg (17.7 pounds).
That is, his body was missing 170 calories every day.
 Harris JA, Benedict FG. A Biometric Study of Human Basal Metabolism. Proceedings of the National Academy of Sciences of the United States of America. 1918;4(12):370-3. Epub 1918/12/01.
 Estimating daily energy expenditure in individuals with amyotrophic lateral sclerosis
Edward J Kasarskis, Marta S Mendiondo, Dwight E Matthews, Hiroshi Mitsumoto, Rup Tandan, Zachary Simmons, Mark B Bromberg, Richard J Kryscio, for the ALS Nutrition/NIPPV Study Group
The American Journal of Clinical Nutrition, Volume 99, Issue 4, April 2014,
 Actually what is calculated is the Basic Metabolic Rate, not the Total Energy Expenditure, the total amount of energy an individual expends per day. Basal metabolic rate is the amount of energy per unit of time that a person needs to keep the body functioning at rest. Some of those processes are breathing, blood circulation, controlling body temperature, cell growth, brain and nerve function, and contraction of muscles. Basal metabolic rate affects the rate that a person burns calories and ultimately whether that individual maintains, gains, or loses weight. The basal metabolic rate accounts for about 60 to 75% of the daily calorie expenditure by individuals.