Running a 5K While Gaining Muscle and Weight

I want to know how I can weight lift and still train for 5k without overdoing it. I weigh 113 lbs and I want to gain 7 more pounds but I also want to train for a 5k run. How can I do both and not lose any weight?

— Isa A

Answer by Dom:

Hi Isa,
Thanks for your question.

What you want is having your cake and eating it too—and honestly, with the right approach, you can get surprisingly close to doing exactly that.

These two goals pull in somewhat opposite directions. Running burns calories; gaining muscle and weight requires you to eat more calories than you burn. A heavy training programme for a 5k will make putting on weight genuinely hard. But the thing is, you do not need a heavy training programme to run a 5k. That is the key insight here.

Let’s cover off on:

1. Principles of Gaining Muscle and Weight
2. Optimal Way to Prepare for a 5k
3. Shortcutting Your 5k Preparation to Assist Gaining Muscle and Weight
4. How to Structure Your Week
5. What to Eat Around Your Runs

Principles of Gaining Muscle and Weight

To gain weight and muscle, you need two things working in your favour at the same time: a solid strength training programme and a consistent caloric surplus. Neither one alone is enough—you need both.

For strength training, I recommend lifting 3–4 days per week, focusing on compound movements: squats, deadlifts, bench press, rows, overhead press. These recruit the most muscle fibres and give you the best return for your effort. Progressive overload—gradually adding weight or reps over time—is what actually drives muscle growth.

On the nutrition side, aim for a protein intake of 1.6–2.2g per kilogram of bodyweight daily. At 113 lbs (roughly 51 kg), that means 82–113g of protein per day. Spread this across meals: eggs, chicken, fish, Greek yoghurt, cottage cheese, legumes, and a protein shake where needed. Protein is the raw material your muscles use to repair and grow after training.

You also need a caloric surplus every single day. The size of that surplus determines how quickly you gain. A surplus of 250–500 calories above your daily needs is sensible—enough to support steady muscle growth without excessive fat gain. Do not underestimate this. If you eat at maintenance or below, your body simply will not have the resources to build new tissue.

Optimal Way to Prepare for a 5k

The optimal way to prepare for a 5k depends entirely on how serious you are about your finishing time. If you want to be genuinely competitive, you would need significant weekly mileage—high easy-running volume, a long run of 10+ miles, and a mix of tempo, interval, and goal pace workouts. You can read more about all of this on the 5k Running Tips page.

But here is the honest truth for your situation: that level of training is completely incompatible with gaining weight and muscle. High-volume easy running burns a large number of calories—a 3-mile run burns 300+ calories—and doing that four or five times per week makes creating a caloric surplus very difficult indeed. It also places a significant recovery demand on your body, which competes directly with muscle repair and growth.

The good news is that you do not need all of that to simply run a 5k. A 5k is 3.1 miles. It is not a marathon. With a sensible, targeted approach, you can be ready for one without derailing your muscle and weight goals. The trick is choosing the right type of running and keeping the total volume low. You can also explore the Running Workouts page for ideas on structuring faster sessions.

Shortcutting Your 5k Preparation to Assist Gaining Muscle and Weight

My advice here is straightforward: limit your total running volume and make the running you do count. Two to three short running sessions per week, each lasting 20–30 minutes, is plenty when your priority is gaining weight and muscle. Keep easy running to a minimum and use HIIT—high intensity interval training—as your primary running format.

A good HIIT session for your purposes might look like this: warm up for 5 minutes at an easy jog, then alternate 30 seconds hard / 30 seconds easy for 15–20 minutes, then cool down for 5 minutes. You can also use longer intervals: 1 minute on / 1 minute off. Both formats work well.

Here is why HIIT is particularly suited to your situation. Research published in the Journal of Applied Physiology has shown that concurrent training—combining weight training with interval-format running—does not impair muscle protein synthesis or hypertrophy. The feared “interference effect” between strength and endurance training is largely avoided when the running is done in HIIT format rather than long steady-state sessions. HIIT stimulates muscle protein synthesis and builds aerobic fitness with far less total volume than easy running does. It is also more of a muscle builder in its own right. This is the type of running that supports your goals rather than working against them.

Will this get you a personal best time? Probably not. But it will get you to the start line—and across the finish line—of a 5k without sacrificing your muscle and weight goals. If finishing the race comfortably is the aim rather than hitting a specific time, this approach is perfectly sensible.

How to Structure Your Week

A practical weekly structure is the difference between reaching both goals and burning out trying. Here is what I recommend for someone in your position:

• Monday: Weights (upper body focus)
• Tuesday: HIIT run — 25 minutes total (warm-up + 15 min intervals + cool-down)
• Wednesday: Weights (lower body focus)
• Thursday: Easy jog, 20–25 minutes at a comfortable pace
• Friday: Weights (full body or upper body)
• Saturday: Rest or very light activity (walk, stretch)
• Sunday: Rest

A few things to note about this structure. Do not do a hard run the day after a heavy leg session—your legs simply will not cooperate, and the risk of a niggle goes up significantly. If you prefer to run on different days, that is fine, but keep this principle in mind: legs need recovery time after heavy squats and deadlifts.

If you can separate your weight session and running session on the same day—weights in the morning, run in the afternoon or evening—that is actually a good arrangement. It gives your muscles a few hours to begin recovery before you ask them to do more work. That said, it is not essential if your schedule does not allow it. Running after weights on the same day is manageable when the running session is short.

One full rest day each week is non-negotiable. Your body builds muscle during recovery, not during the sessions themselves. Treat rest as part of the programme, not a gap in it.

What to Eat Around Your Runs

This section may be the most important of all for your goals. Running burns calories—and if you do not replace them and then some, you will not gain weight. Simple as that.

A 20–30 minute HIIT session burns roughly 200–300 calories. You need to eat those back, plus maintain your daily caloric surplus. On running days, your total calorie intake will need to be higher than on rest days. Plan for this rather than leaving it to chance.

Protein timing is a secondary concern compared to your total daily protein intake, which is what actually drives muscle repair and growth. That said, I’d still like you to have a protein-rich meal or shake within a couple of hours of finishing each session, particularly if you trained without eating beforehand. A simple option is a shake with 25–30g of protein after training, followed by a proper meal in the hours that follow. Hitting your daily protein target matters far more than hitting a precise window.

Do not skip carbohydrates. You need carbs to fuel your runs and replenish your glycogen stores afterward. Rice, oats, potatoes, bread—these are your friends. The trick is eating enough of everything, not restricting any one thing. At 113 lbs with an active training programme, you may need to eat more than feels natural. Build up gradually and track your weight weekly. If you are not gaining, eat more. :)

Stay consistent, keep your running volume sensible, and let the weights and the food do the heavy lifting—quite literally.

Kind regards,

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