Do people with slow metabolism tend to gain weight (fat) if they stop exercising?

Question

So, my height is 5'4" and I weigh around 83 kg which gives a pretty bad ratio of BMI. My Triglyceride level is 238 mg/dl (desirable amount should be <160), HDL Cholesterol is 31 mg/dl (borderline limit is 35-60), LDL Cholesterol is 89 mg/dl (Desirable limit should be <130). My TSH level is borderline, which is, 6.72 μIU/ml (Among adults, it should be 0.27 - 4.2). My cardiologist recommended me a 1400 Calorie low-fat diet.

I don't know for sure if my metabolism is slow (naturally), but it is a fact that I have been obese since childhood. In 2016, I lost 12 kg of weight through diet and exercise. However, because of some circumstances, I had to quit exercising for over a year (almost). I gained whatever I lost through diet and exercise. So, I went to a dietician. She gave me a chart and she said that I should not join any gym and should rather walk for 1 hour, everyday. I asked her that why is joining a gym and exercising there a problem? She said, that people who unjoin a gym for whatever reasons, later, end up adding weight (fat).

Is it true? And if so, is it because of their slow metabolism rate or is it because they don't trim down their diet after unjoining a gym? I could not find any evidence for her claims, so any help in this regard will be helpful.

P.S. When I used to work our earlier, I used to do 30 minutes of cardio followed by 1 hour of strength (resistance) training.

Answer 1

I don't see how walking on a treadmill in a gym is any different than walking outdoors, with respect to caloric expenditure. Since people who join a gym tend to stop exercising entirely if they stop--in other words, they stop going because they stop exercising, not because they found somewhere else to exercise--the dietician's claim as you have characterized it, is misleading, because it seems to attribute weight gain to gym attendance, rather than lack of exercise. Metabolism has little, if anything, to do with it. Metabolic rate will slow down if you starve yourself for prolonged periods of time. High intensity, daily cardiovascular activity will increase metabolic rate, but many people cannot sustain that kind of training over a long enough period.

That said, walking outdoors is free. A gym is (usually) not. Walking outdoors can be integrated into other activities of daily living. About the only activities you can integrate into walking on a treadmill is watching television or reading a book.

As for an exercise plan, weight training should not be your priority. A modest caloric deficit in conjunction with regular and consistent cardiovascular exercise, that varies in intensity, will be most effective. It is important not to decrease caloric intake too much at once, but to do it gradually just as one should ease into a new exercise routine gradually. Consistency is absolutely necessary. As you begin to see progress, supplement with some weight training, because cardio gets easier as you lose weight and your body adapts to the stress--and it does this remarkably quickly in the initial stages even if you don't notice the weight loss.

One hour of brisk walking is about 3 miles (5 km). That may seem like a lot every day, but without a caloric deficit, it will only improve cardiovascular fitness and will not result in weight loss. You may expect to only burn maybe 300 calories for that hour of walking, which is only a small fraction of the energy content in the food an average adult needs each day. One candy bar can be around 200 calories. A few small cookies can add up to 300 calories. Two 12-ounce cans of non-diet soda is already nearly 300 calories. So, eliminating snacking and sugary, fatty foods is going to be the bulk of where your weight loss success will come from, because no amount of daily exercise you can do right now can compensate for a caloric excess.