Two years ago, a report was published in the British Journal of Sports Medicine suggesting that while exercise can reduce the risk of developing type 2 diabetes, cardiovascular disease or neurodegenerative disease, it does not help with obesity or to prevent long-term weight gain.

The authors of the review, Drs Aseem Malhotra, Tim Noakes and Stephen Phinney, who are fervent advocates of elimination diets for metabolic problems and weight maintenance, argue that diet is the single most effective public health intervention and that regular physical activity should perhaps come second.

While it is true that obesity is about much more than an unhealthy lifestyle, if we look at this from an ancestral health point of view, we evolved as a species outdoors and we moved to live. Shouldn’t we bring back these considerations into the way doctors work with overweight patients?

At a time when we’re learning that so many risk factors for different diseases are easily modifiable through both dietary and lifestyle interventions, exercise represents a tool that can improve health outcomes and weight management when structured correctly.

Although it has been said that exercising is almost useless for weight loss, research actually suggest that resistance training as opposed to aerobic exercise – used in most trials of exercise – can be very powerful when done in combination with diet.

Calling into question the importance of exercise negates a whole host of other important health benefits linked to working out, like improving insulin sensitivity and cardiorespiratory fitness, the recruitment of fast-twitch muscle fibres to reduce the risk of sarcopenia, an increased sense of wellbeing and reduced anxiety.

The health effects of physical activity

Long before it helps build muscle, burn fat and make us all into happier, healthier people, exercise changes the way our bodies work at a molecular level.

Firstly, exercise does great things to insulin sensitivity, regardless of diet quality. As one begins to exercise, insulin production gets down-regulated and can still operate in the background at a lower rate.

For example, a single session of resistance exercise has been shown to enhance insulin sensitivity for many hours after exercise. Even low intensity exercise, such as brisk walking, can increase the body’s insulin sensitivity.

A recent study has also found that exercise turns on autophagy in muscle mitochondria (mitophagy). Mitophagy, which is part of the body’s innate “recycling program”, is a process well documented for its potential protective effects against the development of insulin resistance and type 2 diabetes.

Interestingly, one study also found that there are exercise-induced changes happening in monocytes – an important immune cell that circulates in the bloodstream. This has been linked with a reduction in unnecessary inflammation which promotes insulin resistance.

Diet quality, energy balance, obesity and weight gain

The science of obesity is moving away from simplistic ideas of energy balance, willpower and calorie counting toward the elucidation of effects of foods and diet patterns as determinants of long-term weight regulation.

Total calories do matter in the short term, which is why people can initially lose weight on nearly any type of diet by cutting calories. However, for long-term weight maintenance and for cardiometabolic health, healthful food patterns are most relevant.

The quality and types of foods consumed influence diverse pathways related to weight regulation, such as satiety, hunger, brain reward, glucose-insulin responses, hepatic de novo lipogenesis (carbs stored as fat), adipocyte function (like our fat cells’ capacity to expand, metabolic expenditure (eg, the thermogenic effects of foods), and the microbiome.

Thus, all calories are not equal for long-term weight gain: certain foods impair these pathways, others have relatively neutral effects, and others promote their integrity. Diet quality also influences the propensity toward excess abdominal fat, which from the data produces the largest metabolic harms.

It is important to note that the metabolic harms and weight gain associated with high-carb diets, talked about at length in the report, are appreciably larger in those with pre-existing conditions like insulin resistance or atherogenic dyslipidemia, and smaller in younger, lean individuals with no metabolic derangements and high physical activity.

Being active to prevent gradual weight gain

US studies suggest that the average adult gains only about 1lb (0.45 kg) per year, consistent with habitual excess energy intakes sometimes as small as 50 kcal/day, which explains the gradual weight gain seen in many people.

When sustained over many years, this seemingly minor energy excess and annual weight gain drives obesity, for eg, leading to a 10 lbs weight gain over 10 years, 20 lbs over 20 years, and so on.

While it is sometimes hard to find time to fit in a full workout into our daily routine, anyone can carve out some short forms of exercise, like a brisk walk, a quick jog or some push-ups, to help offset daily excess energy intakes.

What it means for you

Although you might not see the changes you want immediately with regards to weight loss, even gentle exercise can induce important changes taking place inside our cells that play a role in protecting us from heart disease, type 2 diabetes and other conditions.

With that being said, even though exercise has far-reaching health benefits and can help you lose weight in the short term, how much and what you eat greatly affects weight maintenance in the long term.

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