Boy is that a combination of specialties. I applaud your interest in nutrition.
My calculator’s formulas are proprietary but suffice to say they follow current nutrition science and practice. You could probably get a similar result if you had a registered dietitian do the math for you or if you had a reliable nutritional assessment software program. Unfortunately, most nutrition software programs do not utilize a dietitian for design and many greatly over or underestimate caloric needs or exercise expenditure. There are numerous formulas out there for estimating caloric needs and I employ the most reliable according to research. Since my formulas are proprietary, I’m sorry, I cannot reveal what they are nor where in the literature you could find the basis for these formulas. BTW, I have been designing nutrition software since 1989. I have spent a great deal of time researching formulas in the literature, making these formulas work realistically in a computer environment and trying them out on real people.
I have a bachelors in dietetics with a minor in chemistry from Univ of N Colorado in Greeley and a masters in nutrition with a minor in counseling and guidance from North Dakota State University in Fargo. I am a registered dietitian with the Academy of Nutrition and Dietetics and licensed dietitian in the state of Minnesota. Many states require licensure of any person providing dietetic or nutrition services and usually states provide reciprocity. I have worked as a clinical dietitian for over 26 years. You can read further about my work experience in my bio at https://www.dietitian.com/bio.html or clicking on my name in the Ask the Dietitian banner on my home page.
BMI is an estimate of percent body fat. You are not 50% fat! I am testing a new calculator that will display a person’s BMI result and yours is 41.
Your healthy body weight range is 160 to 196 pounds and a healthy BMI is less than 30. Would recommend a realistic weight goal that you could achieve in 1 month otherwise, focusing on a long-term goal may be too far in the future. Why not start out with a 10-pound weight loss one month from today?
Research has shown that weight loss to an “ideal body weight” is no longer necessary. Some of the health risks associated with weight gain can be reduced with a mere 10 – 15% weight loss. So, at 305, your health risks would be reduced by losing 30 – 45 pounds, not down to 180 pounds.
Wrong assumption about the relationship between body weight and body fat. At 305, you could be a linebacker for the Green Bay Packers and be 9% body fat. You could still be 41% body fat at 180 pounds if all you lost was muscle during weight loss, especially if you lost weight very quickly on a very low-calorie diet (semi-starvation ketosis diet). How you exercise during weight loss and how fast you lose weight determines the composition of the weight you lose. Most people lose some fat and some muscle with weight loss. If you want to preserve your current muscle mass and lose more fat, you need to follow a very gradual 1 – 2 pound per week weight loss and participate in aerobic and weight lifting exercises daily.
If my calculator gave you an estimate of 3630 to maintain your weight at 305 then it would recommend 2630 (not 2480) to lose 2 pounds per week. It does not allow a 3 pound per week weight loss because research has shown that weight loss greater than 1 – 2 pounds per week is quickly regained once a quick weight loss diet is ended.
Calorie needs are dependent on body weight as one factor. As you lose weight, your calorie requirements to maintain your weight at a lower weight will be less. Therefore, you should come back and re-enter your lower weight into the calculator with about every 5 to 10-pound weight loss to get a new calorie level that will support continued weight loss. Otherwise, you will plateau periodically in your weight loss efforts. This is my perspective of long term weight loss, but one calorie level will not continue to achieve weight loss at 305 pounds and 250 pounds or 180 pounds simply because fewer calories are needed to support 250 pounds than 305 pounds. Go back and see what your calorie recommendation is at 300 and 295 pounds respectively to see what I mean. You will only see a 50-calorie difference between weighing 305 and 300 pounds. So, 1 pat of butter (45 calories) extra a day can make the difference over time between weight loss and weight maintenance. Surprised?
If you have become less physically active, why not try water sports as they don’t put pressure on knees and other weight bearing joints? You certainly could walk around a pool or do you swim? You were a very active person if you ran the NY marathon. What changed your exercise habits? Only osteoarthritis?
Actually, body fat (white fat) is pretty inert and just sits there as a repository for stored energy (calories) compared to metabolically active (read burns calories) muscle tissue. Brown fat located in a person’s chest is metabolically active in producing heat but does not proportionately comprise 1/3 of all body fat. The amount of brown fat differs from person to person and is often higher in persons who seem to eat and never gain weight. Sorry, there isn’t anything you can do to increase brown fat and decrease white fat. On the other hand, muscle tissue as you know comprises both organs and muscles that perform work.
Your calorie level at 2130 sounds a bit aggressive for long term success and your exercise plan may stress osteoarthritic knees which aren’t going away just because of weight loss. Also, you forgot to factor your exercise program into your calorie calculations. Remember that any exercise you start will add to your calorie deficit and increase the speed of weight loss, However, since muscle weights more than fat, you may see a slower weight loss after initiating an exercise program (especially strength training that adds muscle), so don’t get discouraged if you don’t lose weight as quickly as you anticipate.
Remember to consult with your private physician before starting an exercise program. Hope you chuckled, but at your weight and age, it would be a very good idea to have complete physical if you haven’t’ had one in a while.
Lastly, remember that eating is not an exact science and weight loss is not a linear equation. To achieve your daily calorie goal, you will need to write down everything you eat and keep track of calories. You can do that either with a good nutrition software package or the Diabetic Exchanges. Also, what meal plan had you thought of following other than fruits and vegetables with < 30% fat? Considering the time, you have spent planning your energy needs, you should have a meal plan for guidance. Being a physician, I'm sure you frequently refer your patients to other specialties. Have you considered referring yourself to a registered dietitian for weight counseling / meal planning and an exercise physiologist for exercise / strength training?