11 December 2019
The Flux Capacitor: Increasing Energy Flux To Maintain Your Weight Loss
It’s not often that you find a paper that you really sink your teeth into, the brain juices get flowing, you crack out the highlighter…pour a packet of pretzel M&M’s onto your desk. But this paper was one of them for me. Brand new, just published in October. At completion of a weight loss diet,…
It’s not often that you find a paper that you really sink your teeth into, the brain juices get flowing, you crack out the highlighter…pour a packet of pretzel M&M’s onto your desk. But this paper was one of them for me.
Brand new, just published in October.
At completion of a weight loss diet, possibly the biggest concern we have is how the hell do we maintain it? The technical answer is to maintain energy balance at the reduced body weight by either coupling lower daily energy intake with a low daily energy expenditure (termed low energy flux energy balance) or by pairing a higher energy intake with a higher energy expenditure (high energy flux energy balance).
Logically, it wouldn’t matter whether we maintained energy balance with a low flux or high flux approach. But things aren’t that simple.
Given the environment we live in is characterised by a plethora of highly energy dense, palatable, readily available food products, and a lack of need for daily movement or activity (office jobs, vehicles, elevators, uber eats to name a few…), it can be particularly difficult for weight-reduced individuals to maintain energy balance in a low flux state. In most cases, weight-losers will struggle to maintain the new body weight from an inability to sustain the required level of food restriction, resulting in an increase in energy intake, re-establishing high energy flux, but at or near the original body weight. Additionally, leaning on anecdote, while working with a number of sports athletes who are consistently in a high flux state, I’ve been surprised at times by the relative ease the large majority of these athletes can maintain a lean physique year round with comparatively minimal dieting effort, compared to your traditional physique athlete in a lower flux state, who has to fight tooth and nail to avoid spiralling up in body fat during the off-diet phase of the season. So perhaps there is something here worth digging into…
In this new study, it is proposed that after a weight loss diet, increasing physical activity substantially can re-establish a high energy flux state (high energy intake and high energy output) but without significant weight regain, and therefore is a preferable alternative to low energy flux weight maintenance efforts. This is interesting, given the extreme commonality (and perhaps even recommendation) for dieters and coaches within the fitness industry to “cut cardio” quite drastically in the weeks following a “prep” or weight loss diet. Additionally, it certainly does not align with bodybuilding lore to avoid cardio like the plague during the off-dieting season.
I’m going to touch on some of the major points made by the authors which might help to twist your perspective in regards to why it might matter how energy balance is attained (especially post diet), and why net energy balance (irrespective of the amount going in and out) shouldn’t be our only consideration when transitioning out of a diet.
Metabolic advantages of a high flux state
While I dare say it’s obvious, achieving high energy flux through increasing physical activity is clearly associated with better metabolic function. In one respect, those with high energy flux have greater metabolic flexibility, meaning they have improved ability to match fuel utilisation throughout the day in response to changes in feeding and activity/exercise. Benefits of this include improved fuel supply for immune cells, maintenance of adequate circulating glucose levels, efficient flux of fatty acids into the liver for increased ketogenesis when required, and the ability to quickly increase oxidation of fuels following an overload of macronutrients. Thus, someone who is metabolically flexible has the ability to rapidly adjust to periods of fasting, feeding and high levels of physical activity in a more efficient manner than someone who is less metabolically flexible.
Appetite advantages of a high flux state
Research has suggested that high levels of physical activity are associated with better regulation of energy balance, meaning a closer pairing of energy intake to energy expenditure. Individuals in sedentary occupational jobs were shown to consume as much energy/calories and have higher body weights compared to those performing heavy active work. Instinctively, higher daily energy expenditure characteristic of a high flux state would surely result in better regulation of energy intake in the midst of our obesogenic eating environment, due to the requirement of greater energy intake required to maintain energy balance. While some individuals might exercise so they can eat more food with less restriction, the benefits of higher physical activity to body weight management go beyond the opportunities for greater food indulgence. In previous studies, increased physical activity has been associated with greater meal-induced satiety and better appetite regulation. In a recent experimental study, it was reported that high energy flux over a 3-day period from treadmill walking resulted in acutely greater appetite control, whereas low energy flux resulted in an energy surplus of 17.5% during ad libitum intake. Additional studies have given further evidence of appetite dysregulation at low levels of physical activity/low energy flux. In a room calorimeter experimental study, they found that men expending 1.4 × REE in a sedentary condition for seven consecutive days ingested as much food energy as when they were more active, expending 1.8 × REE for the 7 days in the calorimeter. They concluded that reducing physical activity fails to result in a compensatory decrease in energy intake.
What about increasing energy flux with more weight training?
It is generally accepted that the net energy cost of resistance exercise bouts is typically lower than an equivalent amount of time spent in moderate intensity endurance exercise. For most lifting sessions, more time is spent recovering between sets than the time spent performing the number of repetitions within a given set. Thus, this mode of exercise might appear to be of lower importance for individuals seeking to increase daily energy flux following weight loss.
Impact of high or low energy flux in weight maintenance studies
Observational studies of participants enrolled in weight loss studies have shown significantly higher levels of physical activity (higher energy flux) in weight loss maintainers compared to weight re-gainers. In a recent case-control study, they found significantly higher levels of physical activity in those individuals who maintained weight loss compared to controls with or obesity.Importantly, other studies have shown that participants in a high flux period reported significantly lower hunger and greater fullness compared to their days spent in low flux, despite being in energy balance across the two different flux conditions. These data support the concept that at higher levels of energy flux owing to greater physical activity, appetite is likely to be regulated more accurately to match energy output and minimize the potential for weight gain.
- Most people who willingly lose weight will need to re-establish energy balance (energy in meets energy out) at the reduced body weight
- This can be achieved using a high flux (high energy in and out) or low flux (low energy in and out) approach
- Establishing a high flux state by increasing physical activity can allow a weight-loser a higher, more achievable calorie intake target in an obesogenic environment
- While net difference in energy is the same in a high or low flux state, appetite may be more tightly regulated and matched to energy output, with appetite not driving compensatory eating for the increase in energy burned through activity
- There may be a number of metabolic advantages to re-establishing energy balance using a high flux state i.e. metabolic flexibility
- Research suggests weight loss maintenance is superior in study participants in a high energy flux state post diet compared to low energy flux
- Decreasing cardio and activity post diet might be a bad idea despite going against typical behaviour in bodybuilding circles
- Weight training is not likely to provide the requirements to establish a high flux state, moderate endurance training is better
- Achieving the amount of exercise required to maintain lost weight in a high flux condition is a major challenge, but may be more feasible than sustained food restriction
- There seem to be powerful biological processes and environmental factors opposing food restriction, but little evidence of biological opposition to a high flux state by way of increased physical activity
- For most individuals, food restriction alone is not an effective long-term strategy for weight loss maintenance and that future research efforts should be focused on the interaction of diet and exercise in achieving high energy flux at a healthy body weight