I often hear that we should eat first thing in the morning to “kick start” our metabolism, or eat small meals more often to keep our metabolism going all day.
Eating actually DOES increase our metabolism, this process is called the thermic effect of food (TEF), and it is because the process of digestion requires energy. BUT, it doesn’t matter when or how much food we eat and in fact, eating 1 large meal increases metabolism more than eating several small meals.
How much impact does TEF have on your overall metabolism?
60% of your total metabolic rate is due to your basal metabolism, which os the amount of energy you burn just existing and fueling your cells chemical reactions and cellular processes.
0-10% is accounted for by the amount you exercise.
10-20% is due to calories you burn doing non-exercise activities such as moving around, cleaning, fidgeting, walking, lifting etc. If you are cold then you will burn more calories because it takes energy to make body heat.
10% is due to TEF. This can increase or decrease depending on the types of foods you eat. Eating more plant foods, protein, and whole grain high fiber carbohydrates requires more energy to digest than fat.
Some factors that affect your metabolism :
- Exercise – doesn’t burn as many total overall calories as people would like to believe but it does contribute to your overall metabolism. High intensity exercise burns more than moderate longer duration exercise, and all forms of exercise have multiple other health benefits
- Age, as we get older we tend to burn fewer calories, which is why people can tend to gradually increase their body weight over time if they continue to consume the same amount of food, very annoying for sure, but we can survive on less over time
- Amount of muscle mass – muscle requires much more energy to sustain than any other tissue, it is why our body loses it if we stop using it. It is also why weight lifting is so beneficial for weight loss because increasing your muscle tissue increases your overall basal metabolism
- Being male or female, males burn more energy because they make more testosterone and generally have more muscle mass
- Body size – bigger people have more cells that require energy
- TEF is influenced by:
- meal size – studies have shown that 1 large meal will increase TEF more than 3 small meals (although not a huge significant difference), so you don’t have to eat multiple times per day – food companies want you to though. Some people worry that if they only eat 1 or 2 meals per day they are impacting their metabolism in a bad way, be assured that this is not true. Humans evolved to eat sometimes and not eat other times.
- composition – higher protein, complex carbs containing fiber like whole grains, high fiber foods, and whole fruit and vegetables all increase TEF.
- duration of meals – one study found that people that chew more and take longer to eat a meal will have a higher TEF – it is beneficial to eat slower anyway because there is time for satiation signals to tell your brain you are full before you eat more calories than you need.