Episode 226 – Is It Possible to Boost Your Metabolism?

The following information aims to break down what people mean by “metabolism,” how calorie intake shifts it in the short and long term, and which factors and foods play a role.

Defining metabolism (RMR vs TDEE)

Metabolism is how your body converts food and drink into energy.

Resting Metabolic Rate (RMR): energy burned at rest to run vital functions like breathing and circulation. It can change; it is not fixed.
Total Daily Energy Expenditure (TDEE): the sum of RMR, exercise activity, non-exercise activity thermogenesis (NEAT), and the thermic effect of food (TEF).

When most people say “metabolism,” they often mean a mix of RMR and TDEE. This information covers both.

Thoughts on total calories (short vs long term)

Short term

Eating more calories tends to raise energy expenditure; eating fewer tends to lower it. This adaptive response is often called metabolic adaptation. As intake drops, the body conserves energy—core temperature can dip, hormones can shift, and spontaneous movement often falls. TEF also scales with intake: more food means more energy burned digesting it.

Long term

Research paints a more optimistic picture than the famous Biggest Loser study suggests. In many studies, metabolic adaptation fades once weight stabilises. For example, after a fat-loss phase, participants measured at maintenance four weeks later showed no remaining adaptation. What you’ve done recently matters more than what you did years ago.

Does long-term dieting or yo-yo dieting matter?

Yo-yo dieting—large swings down and up—typically isn’t helpful. In deep deficits, TEF, exercise output, and incidental movement drop, while hunger and food reward can rise, which makes maintenance harder. Building in a phase at maintenance (or slightly above/below) for an extended period can help practically and psychologically.

The Biggest Loser findings (large, sustained RMR suppression ~500 kcal/day years later) appear to be an outlier due to its extreme protocol and very high ongoing exercise. In contrast, bariatric surgery research generally shows RMR in line with predictions after weight loss; one study even found a small increase versus predicted at six months. Overall, when weight stabilises, adaptation typically reduces, and it does not predict weight regain a year later in the study cited.

Thoughts on strategies to increase it like reverse dieting

Reverse dieting (adding ~100 kcal per week for weeks) aims to “build” metabolism. The team’s take:

You don’t need a slow climb to reverse adaptation; jumping to maintenance can work.
Case studies can mislead because people may start still in deficit and end in surplus while weight looks unchanged. That doesn’t prove a 500-kcal metabolic boost.
Even if you “build” metabolism, going back into a deficit for a few weeks shifts adaptation the other way again.
A slower approach can still be useful behaviourally for those who overshoot when exiting a deficit.

Foods that could help

Start with the big rocks that raise TEF and improve absorption dynamics:

Protein-rich foods and high-fibre foods (e.g., whole grains, vegetables) increase TEF more than many other foods.
Minimally processed foods can slightly increase the energy cost of digestion and may reduce calories absorbed versus highly processed options. Shifts of ~100–200 kcal/day are possible when moving from mostly processed to mostly minimally processed patterns.

Then, consider niche options with modest effects:

Capsaicin (chilli): ~50 kcal/day increase with regular intake.
Caffeine: ~50 kcal/day when going from none to a fair amount; habitual use may blunt this.
Green tea/green tea extract: roughly ~50 kcal/day, sometimes up to ~150 in studies.

These exist, but the team doesn’t prioritise them because effects likely diminish over time and appetite often adjusts upward with higher expenditure.

Additional TEF information

TEF is the energy used to digest and process food. It scales with how much and what you eat. More total food raises TEF; higher-TEF foods (protein, fibre-rich choices) raise it further. Consequently, larger meals and higher-protein, higher-fibre patterns push TEF up, while lower intake pulls it down.

Other contributors

Multiple factors influence RMR and TDEE:

Muscle mass: costs more energy to maintain than fat mass. It helps, though building muscle is slow and effortful relative to the metabolic gain.
General activity & fidgeting (NEAT): vary widely and meaningfully. People who fidget more or naturally move more often have higher expenditure.
Exercise: raises overall daily burn and supports weight maintenance.
Age and gender: also play roles in typical formulas.
Genetics: matter as well.

To what extent does genetics matter?

Even after accounting for fat-free mass and common predictors, research suggests ~200–300 kcal/day differences in RMR between individuals that likely stem from genetics. That gap isn’t enormous, yet it’s meaningful. Differences likely widen further when factoring in NEAT.

Overall recommendation

Don’t live in a deficit year-round. Spend time at or near maintenance to reduce adaptation and support hormones, hunger regulation, and training.
Lift and move more. Increase exercise and keep daily movement high to raise TDEE and expand your calorie “budget.”
Eat mostly minimally processed foods with enough protein and fibre. You’ll nudge TEF up and make appetite management easier.
Use “boosters” sparingly. Capsaicin, caffeine, and green tea can add small, diminishing returns.
Avoid yo-yo extremes. If you’ve cycled often, hold maintenance for an extended phase. Reverse dieting can be a behavioural tool, but jumping to maintenance also works.

The bottom line: recent habits drive metabolism more than old history. Focus on sustainable actions that raise or preserve energy expenditure while keeping you consistent.