Dieting and weight-loss is not just as simple as calories-in and calories-out. Metabolism has a lot to do with weight-loss. For example, if a vehicle uses different kinds of fuel it will run more-or-less efficiently, depending on the fuel used. The human body is very much the same… If someone eats calories in-the-form of simple carbohydrates (processed food) then their body will need to expend very little energy metabolising what they eat. If someone eats calories in-the-form of complex carbohydrates (whole foods) or protein their body has to use energy metabolising what’s eaten to turn it into useable energy (glucose). See my post about metabolism.
Another factor to consider is the after-burn effect of strenuous exercise. When someone exercises in zones 2-3 (Zone 2- 65-85%, zone 3 85%+ of a person’s Max Hear Rate – MHR) their body uses stored glycogen in the muscles and liver as they exercise. The body will replace this ‘lost’ glycogen later. Body fat or food is used to replace the used glycogen for a several hours after having stopped exercising (that means using even more calories).
When talking about losing weight what is really meant is reducing the percentage of fat in the body, right? Not trying to lose water, or muscle or bowel contents. From personal experience my scale weight can vary as much as 6 lbs in a 24-hour period depending on what exercise I do and what I eat, drink and bowel motions. Personally, I look at my average weight on a monthly basis now and not daily or even weekly changes.
Someone will lose weight using a calories in-calories-out mentality and whilst maintaining a calorie deficit. Although, without a well planned diet and exercise plan it is easy to quickly gain weight once the ‘diet’ stops. A sustainable diet and exercise regime is key and not a lose weight quick ‘fad’. I would highly recommend doing exercise which, makes your heart beat fast (65% MHR or above). Also making general lifestyle changes to burn more calories as part of a daily routine. Cycling / walking instead of driving, stairs instead of lifts/elevators, standing instead of sitting etc…
BUT more than anything else enjoy the process … it’s about being alive, not punishing yourself (diet & exercise) so you have a ‘body’ that impresses a bunch of people who don’t even care about you!