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“Let food by thy medicine” is a quote often attributed to Hippocrates, the ancient Greek father of medicine. When all is said and done, what and how much you eat is potentially the single most significant element in how healthy you can expect to be.

Likewise, for all gym-related goals, what you put on your plate determines the success you can expect. Here’s a look at how much you should be eating:

Caloric needs are personal

The first point to consider is that someone who wants to maintain their current weight will have vastly different caloric needs to someone who wants to lose or gain weight.

These caloric needs also vary considerably from one individual to the next, meaning that caloric requirements are a very personal matter and can’t be generalised.

The scientific approach to calories

There are scientific methods for calculating the exact number of calories that you should be eating for a given purpose. These are generally pretty tricky and often involve complicated and competing approaches, such as the Mifflin-St Jeor or WHO/FAO/UNU formulas.

There are six biological factors which determine your calorie needs:

Your activity levels – Moderately strenuous physical activity. If you do a lot, you could need thousands of extra calories. If you do none, you may need to eat thousands fewer.

  1. The thermic effect of food (TEF)[1] – Digestion burns calories just like everything else. TEF refers to how many calories are burned digesting your food. This usually accounts for about 10% of the calories you’ve consumed.

  2. Your basal metabolic rate (BMR)[2] – The calories you need just to stay alive. Accounts for roughly 65-75% of your calorie intake on average.

  3. The adaptive component – Changes to your overall metabolism based on how much you overeat or undereat.

  4. Non-exercise physical activity (NEPA)[3] -- Calories burned through non-strenuous physical activity, like getting dressed or carrying the groceries. Varies dramatically.

  5. Non-exercise activity thermogenesis (NEAT)[4] – Calories burned through very low-stress physical activity, like fidgeting. Varies dramatically.

If you plan to follow the most scientific path for determining your calorie needs, get in touch with a professional dietician. Trying using one of the more detailed calorie calculators to give you a rough estimate you can start working with.

The intuitive approach

The intuitive approach to deciding how much to eat is pretty straightforward. It relies mostly on making sure that each meal has a good balance of macronutrients (a protein source, a carb source and a source of healthy fat). In addition, you should stick to whole, natural foods, and routinely compare and adjust your food intake to match your fitness goals.

Here's how that comparison plays out:

  • Contrast your eating habits to your weight gain- Does the way you eat keep you at a consistent weight? Are you steadily gaining weight? Losing it?

  • Consider your weight goals- Do you want to maintain, lose or gain weight?

  • Adjust your eating habits to match your goals- If you’re gaining weight but want to lose it, reduce the size of each meal – for example by serving meals on smaller plates. Adjust each week until you begin to notice weight loss occurring.

A good rule of thumb: focus on your macros first

The three macronutrients are protein, fat, and carbohydrates. Getting enough of these three is essential in order for your body to function properly. One positive approach to meal planning is to focus on getting the right amount of these macronutrients in your diet, from healthy sources, before worrying about calories.

The American Food and Nutrition Board’s suggested Daily Reference Intake (DRI)[5] for carbohydrates is 130g a day for men, non-pregnant or breastfeeding women, and children above the age of one.The DRI for fat is between 25-35g for all men, women, and children above the age of three, while the DRI for protein is 56g for men between 18-70 and 46g for females ages 14-70. Of course, different diets often emphasise different macronutrient ratios for different purposes. Some research shows that athletes and bodybuilders benefit from eating much more protein than advised by the DRI (2.3g per kg of bodyweight compared to the DRI’s 0.8) though other studies find that eating protein above the DRI has no clear effect.[6]

In any case, the DRI is as good a starting point as any. If you find along the way that it doesn’t cater to your personal needs, you can always tweak the ratios yourself.

Handpicked Content: Your handy nutrition guide to healthy weight loss

[1] https://nutritionandmetabolism.biomedcentral.com/articles/10.1186/1743-7075-1-5 [2] http://www.ncbi.nlm.nih.gov/pubmed/16277816 [3] http://www.ncbi.nlm.nih.gov/pubmed/24167194 [4] http://www.ncbi.nlm.nih.gov/pubmed/11101470 [5] https://fnic.nal.usda.gov/sites/fnic.nal.usda.gov/files/uploads/macronutrients.pdf [6] http://www.ncbi.nlm.nih.gov/pubmed/22150425

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