It’s not as sexy as the latest diet craze sweeping through Hollywood, but in the search for a slimmer figure,  slow  and  steady  weight  loss  (one  or  two  pounds  a  week)  really  does  win  the  race.  Whether you want to lose five pounds to fit into your clothes better or need to lose fifty to protect your health as you get older, losing weight boils down to a simple equation: The number of calories you take in must  be  less  than  calories  out.  In  fact,  diet  plans  that  claim  you  don’t  need  to  count  calories  usually reduce  your  calorie  intake  anyway  because  you  eat  smaller  portions  or  cut  out  certain  foods  (or  in some cases, entire food groups).  Even if you choose not to count calories, it’s worth understanding a few key points about them.

Know Your Calorie Needs As You Age

Everyone has a baseline number of calories they need to maintain their current weight, but the number differs according to your gender, weight, activity level—and your age. It isn’t just your imagination; your calorie needs do decline as you get older. Your metabolism slows about 5 percent each decade, so at age forty, women burn about 100 calories fewer per day and men burn about 50 calories fewer than  they  did  at  age  thirty.  That  may  not  seem  like  much,  but  over  a  year  it  can  translate  to  an  extra five  or  ten  pounds.  The  dip  in  your  metabolism  is  mostly  due  to  a  decrease  in  muscle  mass  and  a corresponding increase in body fat , but your organs also use fewer calories as you age.

The best way to determine your calorie quota is by measuring your resting metabolic rate (RMR), the number  of  calories  your  body  requires  for  the  daily  tasks  of  living,  such  as  breathing,  blood circulation,  and  forming  and  repairing  cells.  Your  gym  may  have  a  handheld  device  called  a calorimeter that can measure your RMR pretty precisely. If you don’t have access to a calorimeter, a 2005  review  of  studies  in  the Journal  of  the  American  Dietetic  Association  discovered  that  a  tool called the Mifflin-St Jeor equation is the next most reliable way to estimate a person’s RMR. You’ll need to translate your weight from pounds to kilograms and height to centimeters; the formulas are as follows: 1 pound = 0.45 kg; 1 inch = 2.54 cm